What is Overclocking by rizafani2


									               MYSTERY BEHIND
                        A GUIDE


                       What is overclocking
                       Basics of CPU speed
                    Morale behind overclocking
                       Why not to overclock
                    Goals behind overclocking
                    Overclocking requirements
                    Techniques of Overclocking
                   Bus speed of my motherboard
                           Intel Pentium
                    Cyrix / IBM 6x86 AMD K5
                        Intel Pentium Pro
                   Celeron & Pentium II Cores
                     Overclocking step by step
                        Prelaunch Checklist
                     Trouble shooting HELP !!!
                        And in the end.......

What is Overclocking

                                   A GUIDE FOR OVERCLOCKING / 1
Overclocking in simple term means running your computer's CPU at a speed
higher than what was intended by the manufacturer. Overclocking is
increasing the clock rate of a processor beyond its rating for the purpose of
increasing system speed without buying a new, faster, but more expensive

"Overclocking" is a slang term, and not an engineering or scientific term. The
correct technical terms are "speed-margining" (more common) and
"undertiming" (less common). One can also "overclock" the computer's bus.
The 'overclocking' describes the process of running your CPU at a clock
and/or bus speed that the CPU hasn't been specified for - logically, that speed
is usually higher.

The tempting idea behind overclocking is to increase system performance at
very little or no cost. In many cases you only need to change a few settings
on your motherboard to make your system run faster. In other cases you only
have to add a few components (usually for cooling) to achieve the
performance increase.

In the past, overclocking was usually nothing more than increasing a CPU's
clock speed to that of the next higher model, e.g. a Pentium 120 to a Pentium
133. Now, with new bus speeds available on several motherboards, you can
change the clock and bus speed of a CPU to values that don't officially exist.
This new way of overclocking is yielding an even higher performance increase
than the classic one. It even gives you the ability to increase the performance
of the fastest model of a particular CPU production line (e.g. P200 to 250
MHz, Pentium Pro 200 to 233 MHz).

Basics of CPU Speed

Two variables determine the speed at which your CPU runs: the
frontside bus speed and the clock multiplier. By manipulating these
variables you determine the CPU's clock speed.
Understanding Bus Speed : The CPU uses the FSB (frontside bus, also
called the system or external bus) to communicate with system memory and

         FSB Speed x Clock Multiplier = CPU Speed

         (This is what publicised speed of CPU e.g. Pentium 233
         MHz MMX here FSB speed is 66 MHz and internal speed
         of CPU is 233 MHz using the clock multiplier of 3.5 i.e.
         66 x 3.5 = 233 MHz approx).

The motherboard chipset controls the clock multiplier, which, in conjunction
with the FSB speed, determines the core speed of the CPU. Multiply the FSB
speed by the clock multiplier to get the CPU speed. By manipulating the clock

                                           A GUIDE FOR OVERCLOCKING / 2
multiplier and/or the FSB speed, you can increase the core speed at which
the CPU runs.

Let's start by discussing a 486 processor (these have been around long
enough that most people are familiar with how they work). There are various
breeds of 486 cpu's. The major designations are SX, SX2, DX, DX2, and
DX4. All 486 processors use a 32 bit data bus. The external data bus is how
the CPU communicates with the motherboard. On SX and DX chips the
speed of this bus (FSB Speed) is the same speed as the internal workings of
the processor. On SX2 and DX2 chips the internal speed of the CPU is twice
that of the external data bus i.e. using clock multiplier of 2. On DX4 CPUs the
internal chip speed is three times that of the external bus. The difference
between an SX and a DX chip is the fact that DX 486 chips have a math co-
processor whereas the SX chips do not. Ok, so if you have a 486DX33 that
means the external bus is running at 33mhz. Morover, the internal processing
speed of this chip is 33mhz. A 486dx2/66 also has an external speed of 33,
but the internal workings of the chip double that speed to attain 66mhz. The
"dx2" chips use a technology that takes the external clock speed at which the
motherboard is operating at and doubles it. "SX" and "DX" chips which do not
have the "2" at the end of the name (as in "DX2") do not support a 2x mode of
operation. This should dispel any rumors that one can take a 486dx33 and
turn it into a 486dx2/66 like magic. Similarly, the "dx4" chips have clock
tripling technology built in. This means that again, one may not simply turn a
486dx33 into a 486dx100.

Here is a list of the bus and processor speeds of the most common 486
 Processor Name:       FSB (external)     Internal (processor)     Clock
                       Speed:              Speed:                  Multiplier

 486SX20               20MHZ              20MHZ                    1x

 486SX25               25MHZ              25MHZ                    1x

 486SX33               33MHZ              33MHZ                    1x

 486DX40               40MHZ              40MHZ                    1x

 486DX50               50MHZ              50MHZ                    1x

 486sx2/50             25MHZ              50MHZ                    2x

 486dx2/50             25MHZ              50MHZ                    2x

 486dx2/66             33MHZ              66MHZ                    2x

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 486dx2/80              40MHZ               80MHZ                     3x

 486dx4/75              25MHZ               75MHZ                     3x

 486dx4/100             33MHZ               100MHZ                    3x

 486dx4/120             40MHZ               120MHZ                    3x

 486dx4/133             33MHZ               133MHZ                    4x

 Pent. Ovrdrive 63      25MHZ               63MHZ                     2.5x

 Pent. Ovrdrive 83      33MHZ               83MHZ                     2.5x

So what does all this mean?

Well, the fact is that on many motherboards the bus clock speed of the
motherboard may be set using jumpers or dip switches. I suppose one day
someone asked, "What will happen if I set the bus speed of my motherboard
to 40MHZ despite the fact that I'm using a 486dx33 chip?" This is one of the
types of overclocking; setting the bus speed faster than it really ought to be in
relation to the intended speed of the CPU.

What improvements will I see?

By setting a 486dx33 to a 40MHZ bus speed you will find that the internal
processing speed of the processor directly follows this modification. The chip
will try to operate at 40MHZ. By speeding up the bus speed on a DX2 chip the
internal workings of the chip will still try to double the external bus speed. That
means that a 486dx2/66 operating on a motherboard whose bus speed is set
to 40MHZ will try to operate at 80MHZ. A 486dx4/100 will try to operate at
120MHZ if the bus speed is increased to 40MHZ.

What else can be done?

Some motherboards also allow you to select whether the processor runs
internally at 1x, 2x, 2.5x, 3x, etc. the external bus speed. Additionally, the
BIOS of many systems allows you to modify the number of DRAM wait states,
the cache type and wait states, the ISA bus speed, etc. All of these tinkering
may prove to be of some benefit to overclockers.


                                             A GUIDE FOR OVERCLOCKING / 4
Continuing discussion of above what is reason behind overclocking:
If you are unwilling or afraid to overclock your CPU, there is no reason to
annoy other people with your opinion. Just because the CPU manufacturers
have an opinion on overclocking does not make it the right one. People who
are overclocking their CPUs choose to see it differently and are benefiting
from their opinion. As long as there is no sentence against overclocking, we
are not doing anything against the law.

It is also fairly questionable if there actually is a difference between Pentium
chips with different official clock speeds. The best example of this is the P150
and the P166. Isn't it strange, that all P150s are standard voltage chips and
almost all P166s are VRE voltage chips? Doesn't it sound like Intel is using
the same chip in both of them, but it only runs stable enough at 166 MHz with
VRE voltage. Intel is selling the P150 only to satisfy the market and probably
gets a good chuckle at the stupidity of the general public who don't realize

There are a lot remarked Pentium chips around, as recently discovered when
all over Europe there were several concurrent razzias against criminal
organizations that re-marked thousands of P133s to P166. The proud owners
of these CPUs are convinced they have a real P166, just because it's written
on the chip. Hahaha!! I'm wondering how many people own faked P166s. Did
you know that Intel isn't interested in marking their chips reliably via a
software readout at all? As long as they sell enough chips, they don't mind the
re-marking of Pentiums. They even tried to avoid the publication of the recent
events in Europe and I bet hardly anybody in the US ever heard about that.

The main idea behind sensible overclocking is simply to use your brain, which
brings me back to my 'car driving' introduction. If you want to successfully
overclock your system without any loss in reliability, you will have to take care
of proper cooling, do decent testing, and stay within the bounds of common
sense. Don't try to overclock a P100 to 200 MHz or anything crazy like that.
Just use your brain!
Is smoking immoral? Don’t ask me, ask anyone who smokes!! And yes
smoking is much more closely related to morality than overclocking.

Why not to Overclock - Press CTRL-ALT-DEL to Continue !!

Although there are zillions of tales of damaged CPUs and other system
components, in most cases overclocking is completely harmless. There
are, however, a few things to take into consideration both fatal and non fatal :

                                            A GUIDE FOR OVERCLOCKING / 5
Heat is number one enemy of CPU

The non-fatal one is due to timing. Processors are designed and tested so
that their internal parts will all be ready about the same time, according to
specifications published by their manufacturer. As the heat of the processor
increases above specifications, the internal paths slow down. Some paths
slow down more than others, and eventually there becomes a significant
difference between when something is expected to happen and when it
actually does happen. At this point you may get false information (such as
0+0=1), system lock-ups, or spontaneous resets. This behavior is usually a
signal for you to decrease processor speed or

temperature (see next section).
One fatal possibility is called electromigration. Overstressed ICs can be
slowly destroyed by electromigration. The combination of heat and electric
fields cause metal atoms to wander around under the passivation layer.

Electromigration takes place on the actual silicon chip of your CPU in areas
which operate at a very high temperature, and can cause permanent damage
to the chip. Before you start to panic, you should first realize a few things.
CPUs are designed to run at temperatures between -25 and 80 degrees
Celsius. To give you an idea, 80 degrees Celsius is a temperature that
nobody is able to touch for longer than 1/10 second. I have never come
across a CPU at this temperature. There are plenty of ways to keep the CPU
case at less than 50 degrees Celsius which increases the probability of
keeping the chip inside at less than 80 degrees. Also, electromigration does
not immediately damage your chip. It is a slow process, which more or
less shortens the life span of a CPU running at a very high temperature. A
normal CPU is meant to live for about 10 years. However, in ten years
nobody is going to be using a CPU with today's technology. If you want to be
kept free from this electromigration scare, you have to do as much as
possible to cool the CPU. Cooling is the number one requirement in
overclocking!! Never ever forget that these terms don't necessarily apply for
Cyrix, IBM, and AMD CPUs. Because of the already high rate of heat
production at their original clock rate, you must work extra hard to keep them
cool in overclocked conditions. I've come across several dead Cyrix 6x86
CPUs so far, so be careful or just let it be!

Due to electromigration CPU tend to grow little whiskers at any sharp corner
or irregularity along a trace. Whiskers at different potentials tend to grow
towards each other, much as stalactites grow towards stalagmites in a
limestone cave, because the sharp point accentuates the potential gradient.
In a cave, limestone columns eventually form from floor to ceiling. On a chip,

                                          A GUIDE FOR OVERCLOCKING / 6
you get a short circuit.

(Heat is only a secondary factor in electromigration. The primary factor is
current density in the presence of an electric field. In most digital ICs, the
internal clock signal is distributed by a conductor, usually aluminum, which is
sized carefully for its load. If the clock switches more often than the designer
sized it for, then the clock "trunk" is overloaded and subject to premature
failure due to electromigration.)
The other fatal possibility is simply burning out the bond wires that run from
the pins on the outside of the package to the silicon die of the processor.

Some other problems

Just because your processor will run satisfactorily at the speed it is running
doesn't mean that the rest of your system will. In fact, it is more likely that, if
your system becomes unreliable, it is because other devices are overstressed
by the higher clock speed. Relatively items such as video / disk controllers
and memory, may fail because there is not enough time for them to do their
work when bus frequencies are increased. You can try decreasing bus
speeds, and increase memory wait-states, or you can get faster devices.
Generally, if you get lots of strange errors, such as "No ROM BASIC
installed", try slowing down memory and bus speed.
The other device-based problem is with your motherboard. Every cheap little
component on the board must function reliably at the higher speed or you will
likely experience reliability problems. The only reasonable solution to this
problem is to get a faster motherboard.
Nobody likes system crashes or hangs, but in a professional business
environment, avoiding a system crash or hang can be most crucial. It certainly
is a fact that you are increasing the probability of system faults by
overclocking your CPU. But this is only the probability !! If you have just
overclocked your system and the first thing you do is use it to start writing
your dissertation, don't be surprised if a system crash occurs which causes
you to lose all your data. After finishing the overclocking process you have to
put your system through a tough and thorough testing procedure. If the
system passes all the testing, only then can you talk of successful
overclocking and feel confident everything is working well.
The third debate against overclocking is that your father, brother, best friend,
neighbour, or boss thinks it's immoral. (Is this morality important today when
we have paid many times price and obsolescence monster is catching up
ultra fast).

Correct Overclocking - The Goals

First and foremost, we want to
         improve overall system performance

                                             A GUIDE FOR OVERCLOCKING / 7
         system to be just as stable
         keep our CPU alive!!
The best way to improve system performance is to increase the bus speed. If
you can't do that, either because your motherboard doesn't support higher
bus speeds or your RAM or your PCI devices aren't up to it, you can change
the multiplier instead. Don't expect much gain in performance, however, if you
increase the multiplier but you decrease the bus speed!!! For example,
changing from 166 @ 2.5x66 MHz to 180 @ 3x60 MHz will actually decrease
your overall performance. The same rule applies to changing from 133 @
2x66 to 150 @ 3x50. These types of changes will not make your system any

This is some touchy news for 6x86 users, who should really only overclock
their CPUs to a slightly higher speed than the original. The 6x86 only has
multiplier options for x2 and x3. Don't let yourself be told otherwise!! Of course
you can try jumpering the board to all of the different Intel Pentium settings,
but it won't make a difference for the 6x86 CPU.

Overclocking Requirements

Three things are necessary for overclocking:

The CPU : HA HA HA !!!
So far, Intel manufactures the CPUs with the highest quality, hence the
probability of a successful overclocking is highest with Intel CPUs.
Check to make sure your Pentium isn't faked. If you can peel off a black
sticker underneath the CPU, it's definitely a re-marked one. In this case your
CPU is most likely already overclocked.

The Motherboard
The quality of the motherboard is crucial for successful overclocking! Due to
the fact that the CPU produces fewer 'clean' signals in overclocked mode,
reflections and other flaws on the bus can cause the system to crash or hang.
The reverse situation is also true - in overclocked mode the CPU is more
sensitive to unstable signals from the bus and will crash if the motherboard
can't deliver clean signals. Always go for a branded motherboard!
You will have to decide if you want to go for a higher bus speed or if you will
stick to a maximum of 66 MHz.
The board should obviously support a wide range of CPU supply voltages.
Minimum are 3.3 and 3.45 V, for STD and VRE voltage. If you want to use
P55C, M2 (the new M1/6x86), or the new K5/K6 CPUs, you will need support
for 'split voltage'. This means that the core of the CPU requires a lower supply
voltage than the I/O ports of the CPU. The latest boards all support 2.5 up to
2.9 V in 0.1 Volt steps. If the board offers you an even higher voltage than
3.45 as well, you should be happy, because this might be the last trick to get

                                            A GUIDE FOR OVERCLOCKING / 8
your CPU successfully overclocked.


This topic is new, but it is very important indeed. You will have to consider
decent RAM if you want to run your system at bus speeds of more than 66
MHz. If you want to run an HX board, such as the Asus P/I-P55T2P4 at 83
MHz bus speed, you will require high-end EDO. I've experienced myself, that
the marking of the RAM is less important than it's brand. Be careful, however,
that you don't get second-rate chips from the manufacturers being sold in
some stores. These chips still say Siemens, Micron, or whatever on them, but
their quality won't live up to your expectations. In the case of high bus speeds
always go for SDRAM if you can. SDRAM relieves a lot of the worries of
running at 75 or especially 83 MHz, and runs flawlessly in any case.

The Cooling

I can't proclaim it often enough, the cooling of the CPU is extremely
important ! If you have been able to boot your system with an overclocked
CPU but it crashes within the first minutes, it's most likely due to insufficient
cooling of your processor. Don't think the average small heat sinks with their
small fans designed for a Pentium are able to do this job properly! Their job is
only to keep a normally clocked CPU cooler in case you have very hot
surroundings (e.g. SCSI or Video cards, which can get very hot as well). They
are not designed to save your overclocked system from crashes due to
overheating. This doesn't mean you always have to have better cooling. If
you've got a new SSS CPU, using the 0.35µm die, it just won't get that hot.

If your CPU is of the old 0.6µm die size type, however, you will require decent
cooling. To accomplish this, you can use heat sinks, fans, or both, peltiers, or
peltiers with fans. Peltiers are elements which transport heat using an
electrochemical method from one side of the element to the other, consuming
energy. You will still need a heat sink to dissipate the heat from the non-CPU
side of the peltier and most likely will also require a fan.
My opinion is that you should go for a heat sink, and most importantly THINK
BIG !! If a big heat sink still can't do the job, add a fan on top of it. If you
achieve this cooling effect, you can be sure that any crashes which do occur
are not a result of overheating. So how to get a decent heat sink ? Don't even
think of finding anything in a normal computer shop. You'll find professional
heat sinks only in professional shops which sell electronic equipment such as
transistors, resistors, chips, etc. (e.g. Hobby Electronic Stores).

You can tell how good a heat sink is by looking at the K/W value. K/W
means degree Kelvin per Watt of power dissipation . K/W tells how hot the
heat sink gets per each Watt of heating power of the device it's meant to cool.
If you were able to follow that, you will understand that the smaller the value,

                                            A GUIDE FOR OVERCLOCKING / 9
the better the heat sink. If you can get a heat sink which has a value below
1K/W, you've found a good one. You'll need to make the surface of the heat
sink that will attach to the top of the CPU match the size of your CPU (maybe
the electronic shop will cut it for you, otherwise you'll have to do some sawing
and grinding). Be careful that this surface stays completely flat, so that there
are no gaps between the heat sink and the CPU surface. Finally, you only
need to affix the heat sink to the CPU which is best done with some thermal
compound (also available in every electronic shop). You can also use super
glue, but it should be applied very sparingly with just enough to attach the
heat sink. Do realize that you might not be able to remove the CPU from the
heat sink if the super glue is good stuff. If required, attach a good (powerful +
quiet) fan to the top of the heat sink (how, I will leave this up to your

You should also use besides these hardware solutions some software
solutions like Rain , Waterfall or CPU Idle. These utilities execute halt
instruction during the idle priority thread and thus keeping the CPU cool. I
recommend use of Waterfall because of small footprint, no VXD's, no drain
of any system resources and above all it's free.

Correct Overclocking - The Techniques

Changing the bus Speed : To understand how you can overclock a
Pentium, Pentium Pro, 6x86, or K5 CPU, it helps to realize that the internal
clock in these CPUs runs at a different speed than the external clock or bus
speed. The external clock is the speed at which the cache and the main
memory run and when divided by two yields the speed of the PCI bus. There
are only four different official bus speeds used by the Intel Pentium, Pentium
Pro, Pentium II and the AMD K5 CPUs - 50, 60, 66 and 100 MHz (new
models). The 6x86 uses five bus speeds: 50 MHz, 55 MHz, 60 MHz, 66 MHz,
and 75 MHz. There are also new boards available which support the unofficial
bus speed of 83 MHz. To change the bus speed, look in your motherboard
manual for something like 'CPU External (BUS) Frequency Selection' - these
are the jumpers you will have to change. If you are lucky and happen to have
a motherboard with the new SoftMenuTM technology, you can change these
settings in the BIOS setup menu right from the comfort of your chair. You
don't even have to open the case. Always go slowly and increase the bus
speed one step at a time (e.g. go from 60 MHz to 66, not 60 MHz to 75). This
is the most successful way to overclock. Using this method, almost every
P150 CPU runs at 166 MHz and most all 6x86 P150+ CPUs run at a P166+
level or 133 MHz.

Changing the Multiplier: The internal clock is controlled by an internal clock
multiplier in each CPU which is programmed via CPU pins. Intel Pentium
CPUs support the following multipliers: x1.5, x2, x2.5 and x3. Intel Pentium
Pro CPUs support x2.5, x3, x3.5, x4. 6x86 CPUs so far only support x2 and

                                          A GUIDE FOR OVERCLOCKING / 10
x3, and M2 supports x2, x2.5, x3, x3.5. The K5 is kind of a difficult fellow
here, because it doesn't seem to be affected by the external settings of its
multiplier. So far it only uses the x1.5 multiplier for each of the PR75, PR90,
PR100, PR120, PR133 CPUs. The new PR150 and PR166 K5 CPUs will use
the x2 multiplier, but it seems fairly likely that you won't be able to change it -
although I have not been able to verify this. To change this setting, find
something like 'CPU to BUS Frequency Ratio Selection' in your motherboard
manual. There are usually two jumpers used to change these settings. Again,
you can do all of this in the BIOS setup menu if you have a SoftMenuTM
motherboard such as the new Abit motherboards.

        CPU ratio selector             BUS Frequency selector
             #1     #2    #3     #4    NO Frequency #5          #6    #7
       3X      ON ON      ON     OFF 66.6M               OFF OFF OFF
       3.5X    ON ON      OFF OFF 68.5M                  OFF OFF ON
       4.0X    ON OFF ON         ON    75M               OFF ON       OFF
       4.5X    ON OFF OFF ON           83M               ON     OFF ON
       5.0X    ON OFF ON         OFF

    The above table and figure shows that what are jumper settings and how
    they can be changed to suit our overclocking requirements. The above
    are however from a motherboard's manual of Pentium II system. The
    'CPU Ratio Selector' shows the ratio of internal clock speed of CPU to
    the external clock speed. Here the FSB (i.e. External Bus Speed) is
    assumed to be 66 MHz (default FSB for Pentium II from 233 Mhz to 333
    MHz). But if we want to increase FSB speed we can do so by simply
    setting the jumpers accordingly. As Penitum II is overclocked disabled we
    can only increase FSB speed which is discussed in later part of this

  Changing the CPU Supply Voltage: You might not like it, but this is
  something which is often required to make the CPU run more reliably. First
  of all, I'd like to stress that the Intel Pentium and Pentium Pro CPUs can
  run at a supply voltage of up to 4.6 V. This, of course, requires serious
  cooling because the chip is producing a lot more heat than usual. I have
  tried this with my own P166 and the chip is still doing fine. It didn't really
  help my problem either, however, since it was the memory that would not
  run reliably at 208 MHz, not the CPU. Often the change from STD to VRE
  voltage is the whole trick to successful overclocking. This is due simply to a
  bigger voltage difference between the digital HIGH and LOW conditions,
  which results in 'cleaner' signals for the CPU and other motherboard
  devices. If you can't run your CPU reliably at one particular clock speed, it's
  always worth considering changing to a higher supply voltage. The silicon

                                            A GUIDE FOR OVERCLOCKING / 11
  of STD and VRE CPUs is identical, so you won't damage your STD voltage
  CPU with VRE voltage, the CPU will only run a little hotter. The Abit IT5
  motherboards offer a voltage which is even higher than VRE, of 3.6 V in
  their SoftMenuTM BIOS CPU setup. I'm running my CPU at this voltage
  and it runs completely stable at 205 MHz @ 2.5 x 68, even as I type this

Which bus speed my motherboard supports?

To be honest, the easiest and most sensible answer to that is: TRY IT OUT !!!
Switch the multiplier to the lowest setting and then put the bus speed jumpers
in all the different configurations. For non mathematical people, there are 2 to
the power of the number of jumpers configurations. 4 configurations for two
jumpers, 8 configurations for 3 jumpers, and so on. Just boot up to the DOS
prompt and run ctcm, or a similar program which will tell you the CPU speed.
You then only have to divide it by the multiplier setting to find your bus speed.
Again, if your motherboard uses SoftMenuTM BIOS, you only have to look in
your BIOS setup menu to find all of the different bus speed settings from
which you can choose.
There is also, however, a different approach:
Motherboards with the PLL chip PLL52C59-14 can run at up to 75 MHz and
they also support the 'turbo frequency' feature, which increases the bus
speed by 2.5% (officially approved by Intel's CPU specifications).
        For 75 MHz Pin 8 via 2.2 k Ohm to 0 V ('0 V' means 'ground' and
        NOT 'disconnected'!) Pin 12 via 10 k Ohm to 5 V Pin 13 via 10 k Ohm
        to 5 V
        For 68 MHz, the 'turbo frequency' for 66 MHz Pin 8 via 2.2 k Ohm to
        0 VPin 12 via 10 k Ohm to 0 V Pin 13 via 10 k Ohm to 5 V
        For 61.5 MHz, the 'turbo frequency' for 60 MHz Pin 8 via 2.2 k Ohm
        to 0 V Pin 12 via 10 k Ohm to 5 V Pin 13 via 10 k Ohm to 0 V
        Measured on the Abit boards IT5H, IT5V, PR5, which all use the
        PLL52C59-14. The PR5 also comes in a version with the PLL52C61-
        01, however, the setting below seems to set the board at 61.5 MHz
        instead of 83 MHz.

Motherboards with the PLL chip PLL52C61-01 can run at 83 MHz bus speed
as well and also theoretically support the 'turbo frequency'. There obviously
is, however, a way of configuring this chip (circuitry), so that it would not run
at 83 MHz. I'm working on that.

These are the conditions:
 For 83 MHz or 61.5 MHz 'turbo frequency' for 60 MHz. Unfortunately this
 depends on the circuitry on the motherboards. Pin 5 via 10 k Ohm to 0 V ('0

                                           A GUIDE FOR OVERCLOCKING / 12
 V' means 'ground' and NOT 'disconnected'!) Pin 12 via 10 k Ohm to 5 V Pin
 13 via 10 k Ohm to 5 V
 For 75 MHz Pin 5 via 10 k Ohm to 5 V Pin 12 via 10 k Ohm to 0 V Pin 13 via
 10 k Ohm to 5 V
 For 68 MHz, the 'turbo frequency' for 66 MHz Pin 5 via 10 k Ohm to 5 V Pin
 12 via 10 k Ohm to 5 V Pin 13 via 10 k Ohm to 5 V

I have measured this on the Asus P/I-P55T2P4 rev. 3 board and was able to
verify the exact same settings on the FIC PA-2006 board. The FKI SL586VT II
or Magic Pro MP-586VIP board also use this chip, but you can't get to 83
MHz. Instead you get the pathetic speed of 61.5 MHz. In terms of jumpers,
this means that you will have to find out which of the three jumpers is
connected to the particular pins. It's circuited via the pull up/down resistor of
10 k Ohm. In case you only have jumpers with ON/OFF positions instead of 1-
2/2-3 positions, the ON condition is the condition for 0 V, and the OFF or open
condition is for 5 V.

This information is only for real freaks who want to get their boards to
75 or maybe even 83 MHz by all means. This way, you might be able to
use the higher bus speeds on boards that only have 4 bus speeds, as
long as this board uses one of these PLL chips. You do the necessary
soldering at your own risk and should only attempt this if you know
exactly what you are doing!!!

There are several motherboards that use one of the two PLL chips,
depending on what was available when the motherboard was assembled. The
Abit PR5 is such a fellow (of course I was unlucky enough to receive a board
with the PLL52C59-14) and it seems the shuttle HOT 557 is another. There
are a few reports of 83 MHz bus speeds with these boards, but most simply
can't run at this faster bus speed. This is a real pity, because both of these
two boards can use SDRAM - the best RAM for the 83 MHz bus speed.

            Special Precautions for 75 and 83 MHz Bus Speed

Using this higher bus speeds includes some important restrictions
which you should be aware of.

The PCI bus runs at 37.5 or even 41.6 MHz. This can lead to several
problems with PCI devices. Typical trouble makers are SCSI controllers,
some video cards, and network cards. SCSI controllers and network cards
often refuse to work at the faster speed, but some video boards just get much
hotter than usual. If you find a way to cool these video cards, you shouldn't
have any trouble. My Diamond Stealth 64 Video VRAM isn't affected at all by
those higher bus speeds. I hope the 75/83 MHz bus speed survey will help us
find out which PCI devices run at higher PCI bus speeds.

                                          A GUIDE FOR OVERCLOCKING / 13
The speed of the EIDE interface included with the chipset is not only
determined by the PIO or DMA modes, but is also highly dependent on the
PCI clock. This is one reason why the EIDE interface is always slower in
systems with 60 MHz bus speed or less. This is also valid in the other
direction, meaning your interface will be faster when you are running at 75 or
83 MHz bus speeds than at 66 MHz. At first this sounds fine, but often either
the interface or, in more cases, the hard disk isn't up to the faster bus speeds.
My HDDs work fine at 75 MHz bus speed, but at 83 MHz I have to reduce the
PIO down to 2. The same is valid for EIDE CD-ROM drives. This could be the
cause if you are running into strange lock-ups in windows.

The Asus P/I-P55T2P4 is one example of a board that does not allow you to
adjust the ISA bus speed. It seems to be a fixed divider from the PCI clock.
This can cause sound cards to run into trouble if they don't like the higher ISA
bus speed. I haven't come across this problem myself yet, but I've heard of
one fellow whose AWE 32 produced strange sounds when running at a faster
speed. If you run into this, increase the ISA wait states in the BIOS setup to
try to remedy the problem.
Let me say again that the RAM type and quality is of great importance. Most
60ns EDO will run fine at 75 MHz bus speed, but for 83 MHz you'll need high-
end EDO or SDRAM (as long as the motherboard supports it).

                          Overclocking the Pentium

Intel's Pentium processor is the most successful CPU ever. Because of that it
has to come first here. The nice thing about this CPU is that it is also the
most overclockable CPU ever. This can be attributed to Intel's increased
quality demands put in place after the floating-point flaw disaster. The
Pentium MMX is just as overclockable as the Pentium Classic, maybe even
better. This CPU normally runs at 2.8V. Most motherboards that offer this
voltage also offer 2.9 or 2.93V. This is only 0.1 V more than 2.8 V and
probably just the right thing for overclock-unwilling Pentium MMX CPUs.
Pentium MMX 200 runs fine with 2.8 V at 208/83 and 225/75 MHz. For 250/83
increase the voltage to 2.9 V and everything works fine.

Default Settings for Pentium

                 CPU Speed FSB Speed Clock Multiplier
                 60 MHz        60 MHz        1.0x

                                           A GUIDE FOR OVERCLOCKING / 14
                  66 MHz        66 MHz        1.0x
                  75 MHz        50 MHz        1.5x
                  90 MHz        60 MHz        1.5x
                  100 MHz       66 MHz        1.5x
                  120 MHz       60 MHz        2.0x
                  133 MHz       66 MHz        2.0x
                  150 MHz       60 MHz        2.5x
                  166 MHz *     66 MHz        2.5x
                  200 MHz *     66 MHz        3.0x
                  233 MHz *     66 MHz        3.5x

* Both for Pentium Classics and Pentium MMX

Please let me put a short note about the so much feared 'overclock
protection' from Intel. So far the only thing Intel has done once was
disabling the CPU pin 'BF1', which is responsible for the multiplier settings
x2.5 and x3. You still can run those P133 at 166 MHz, but only with 83 MHz
bus speed. Now since the message about thousands of remarked or
counterfeit Pentium CPUs has eventually reached the US, Intel has to at least
make some announcements to this counterfeit and overclock protection
again, which they did. However already 2 years back, Intel was claiming to
soon ship their chips with a overclock protection, which never took place. I still
doubt that Intel will invest any money in producing this feature at all. Before
they do that, they should and will have to do something against the remarking
opportunity of their chips. Hence I wouldn't worry at all. Intel will probably
never avoid that their chips can be clocked higher, but they may push the
motherboard industry to produce motherboards that don't offer any
overclocking abilities.

If you've read all the paragraphs above, you'll remember the following things:

Always try to increase the bus speed first if you can.
Don't increase the multiplier while decreasing the bus speed - you won't gain
Try higher voltages and don't be afraid of it!
Avoid the P133 'SY022' and 'SU073' if you can.
Don't buy a remarked Pentium - there are loads of them around!

                                           A GUIDE FOR OVERCLOCKING / 15
The most overclockable Pentium CPUs:

P150 is the absolute winner - it's most likely nothing else than a P166 in
P166 Classic & MMX (and hence the P150) is super for 187.5 @ 2.5 x 75
MHz and in most term runs fine at 200 @ 3 x 66 MHz.
P133 great for 150 @ 2 x 75 MHz or 166 @ 2 x 83 MHz - forget about higher
multiplier settings with that CPU.
P75 most of them run at least flawlessly at 90 @ 1.5 x 60 MHz, many of them
at 100 @ 1.5 x 66 MHz.
P200 Classic & MMX superb at 208 @ 2.5 x 83 MHz, great at 225 @ 3 x 75
MHz, amazing at 250 @ 83 MHz - the CPU for the real speed freaks!

Where do you want to overclock today?

           1st choice       2nd choice      3rd choice      4th choice
           112.5 MHz @ 100 MHz @ 90 MHz @ 1.5 83 MHz @ 1.5
75 MHz
           1.5 x 75 MHz 1.5 x 66 MHz x 60 MHz x 55 MHz
           125 MHz @ 112.5 MHz @ 100 MHz @
90 MHz                                            -
           1.5 x 83 MHz 1.5 x 75 MHz 1.5 x 66 MHz
           125 MHz @ 112.5 MHz @
100 MHz                              -                      -
           1.5 x 83 MHz 1.5 x 75 MHz
           125 MHz @ 133 MHz @ 2 x 112.5 MHz @
120 MHz                                         -
           1.5 x 83 MHz 66 MHz     1.5 x 75 MHz
           166 MHz @ 2 x 150 MHz @ 2 x 166 MHz @
133 MHz                                             -
           83 MHz        75 MHz        2.5 x 66 MHz
           166 MHz @ 2 x 187.5 MHz @ 200 MHz @ 3 x 150 MHz @ 2
150 MHz
           83 MHz        2.5 x 75 MHz 66 MHz       x 75 MHz
           208 MHz @ 166 MHz @ 2 x 187.5 MHz @ 200 MHz @ 3
166 MHz
           2.5 x 83 MHz 83 MHz     2.5 x 75 MHz x 66 MHz
166 MHz 266 MHz @ 250 MHz @ 3 x 225 MHz @ 3 x 208 MHz @
MMX     3.5 x 75 MHz 83 MHz     75 MHz        2.5 x 83 MHz
           250 MHz @ 3 x 225 MHz @ 3 x 208 MHz @
200 MHz                                             -
           83 MHz        75 MHz        2.5 x 83 MHz
200 MHz 290 MHz @ 266 MHz @ 250 MHz @ 3 x 225 MHz @ 3
MMX     3.5 x 83 MHz 3.5 x 75 MHz 83 MHz  x 75 MHz
233 MHz 290 MHz @ 266 MHz @ 250 MHz @ 3 x
MMX     3.5 x 83 MHz 3.5 x 75 MHz 83 MHz

                                         A GUIDE FOR OVERCLOCKING / 16
To get a P166 running at 208 MHz is a tough thing and requires high quality
hardware I hope I'll succeed with SDRAM and the R-534, if I ever should
receive it. There is no excuse for running a P150 at 2.5 x 60 MHz as intended
- this CPU definitely runs at least at 166 @ 2.5 x 66 MHz or 150 @ 2 x 75
MHz, which is even better!!

Overclocking the Cyrix/IBM 6x86

I have mixed feelings about writing this paragraph. One one hand, I promised
you information on this subject ages ago, but on the other hand, much of the
information regarding the 6x86 M1 and the upcoming M2 is about to change.
Nevertheless, I will refer to the good old, well known 6x86 and it's later
stepping versions.
Due to the massive heat production of the older versions (steppings of less
than 2.7) and the overly high heat production of even the latest versions, this
CPU is not as flexible as the Pentium for overclocking. The first important
thing to remember is that you are indeed able to kill your 6x86 with
overclocking. I've never heard of an Intel CPU with this problem, not even a
486, but I have heard several stories of fried 6x86 CPUs. Hence I DO NOT
recommend you overclock this CPU at all. The only reason I don't refrain from
writing about the 6x86 is that I've been promising this information for a long
Overclocking the 6x86 is quite a bit more restrictive than overclocking a
Pentium. This is mainly due to its heat production but also can be attributed to
it's limited multiplier settings of x2 and x3. You can more or less forget about
the x3 multiplier because the only scenario where it makes sense to use it is
at 3 x 50 MHz. Due to the pathetically low bus speed, this is completely
uninteresting in the way of performance. Hence this only leaves the x2
If you really want to overclock your 6x86, think small! Think in small steps!! It
is worth considering just one step up. This means P120+ (100 MHz) to P133+
(110 MHz), P133+ (110 MHz) to P150+ (120 MHz) and P150+ (120 MHz) to
P166+ (133 MHz). The step from the P166+ (133 MHz) to P200+ (150 MHz)
seems to be too big and has a fairly low success rate with quite a high risk of
losing the CPU.
You'll achieve the highest success rate with 2.7 or 3.7 stepping 6x86 CPUs
because they run more stable and produce less heat. Cooling is paramount
for the overclocking of a 6x86, so don't even think about overclocking this
CPU without a HUGE heat sink or a power peltier.
I hope all this will all change with the release of the split voltage 6x86. This
chip will be run at 2.8 V and should result in much less heat production.
Maybe the 6x86 will suddenly turn into a really great overclocking CPU.

Overclocking the AMD K5

                                          A GUIDE FOR OVERCLOCKING / 17
The K5 has been late in arriving, but is proving to be very powerful indeed.
The latest performance figures show fairly nice results compared to the
Pentium and the pricing of the K5 is just wonderful! 'How about the
overclocking then?' I ask, 'after all AMD is the manufacturer of the most
overclocked 486 CPUs in history'. My first overclocked CPU was an AMD
486/40 (to 50 MHz) then an AMD 486/100 (to 120 MHz) and everybody
knows about the beautiful and cheap AMD 5x86-133, which just runs great at
160 MHz and still is faster than many P100 systems.
In my initial experience, the older PR75, PR90 and PR100 K5 CPUs are not
great fellows for overclocking. Most of the time, the system would remain
dead after moving up only one step and these versions share the same
serious heat problem with the 6x86.
The PR120 and PR133, however, seem to be much better candidates. These
two guys run at the same external and internal speed as the PR90 and
PR100!! This proves that the chip inside has been improved and altered.
Obviously these CPUs don't produce as much heat as the first incarnations,
which is one of the first requirements for overclocking. The new PR150 and
PR166 (at 120 and 133 MHz) seem to be of the same design.
Unfortunately I haven't got enough information to tell you anything decent
about successful overclocking of the K5.

Overclocking the Intel Pentium Pro

The Intel Pentium Pro still doesn't seem to be a popular CPU for overclocking.
This is really not fair to the powerful Pentium Pro since this CPU works just as
well as the Pentium for overclocking.
The first letdown seems to be the lack of any available motherboard for this
CPU that runs at a 75 or 83 MHz bus speed. Hence you'll have to stick to the
good old 50, 60 and 66 MHz settings. For the Pentium Pro the same
methods are valid as for the Pentium - first try improving your bus

A Pentium Pro150 or a 180 doesn't deserve to run at the puny bus speed of
50 or 60 MHz. They are screaming to be overclocked to the 66 MHz bus
speed and will reward you with a considerable performance increase and a
high reliability.
Default settings for Pentium Pro

    Pentium Pro at 1st choice                    2        choice
    150 MHz          166 MHz @ 2.5 x 66 MHz -
    180 MHz          233 MHz @ 3.5 x 66 MHz 200 MHz @ 3 x 66 MHz
    200 MHz          266 MHz @ 4 x 66 MHz        233 MHz @ 3.5 x 66 MHz

I admit, that it will be tough, to get a Pentium Pro 180 to 233 MHz and a

                                          A GUIDE FOR OVERCLOCKING / 18
Pentium Pro 200 to 266 MHz, but it's worth a try. The second choices
however work out in most of the cases and the Pentium Pro 150 runs great at
166 MHz. The problem with the Pentium Pro is the difficulty to adjust things.
Here the SoftMenuTM technology is a let down, because it wouldn't let you
choose 233 or 266 MHz. You can't adjust the voltage either, because the
motherboards adjusts it by itself or more by a VRM module. Nevertheless the
Pentium Pro is a worthy overclockable CPU!

                    Overclocking Pentium II & Celeron

                           Default Settings for
                           Pentium II

                 CPU Speed FSB Speed Clock Multiplier
                 233 MHz *    66 MHz       3.5x
                 266 MHz *    66 MHz       4.0x
                 300 MHz *    66 MHz       4.5x
                 333 MHz *    66 MHz       5.0x
                 350 MHz      100 MHz      3.5x
                 400 MHz      100 MHz      4.0x
                 450 MHz      100 MHz      4.5x

* Applicable for Celeron also

 Optimal Speed for Your CPU : Remember, just because your neighbor or
brother or whoever can achieve a certain speed with their identical CPU
doesn't mean that yours should be able to hit that same level. Each and every
CPU is unique. Considering these small cores have 8 million trace routes, it
should come as no surprise that no two CPU cores behave the same under

Intel Pentium II 233 - 300 Core Codename Klamath

Intel's first Pentium II CPU had the codename 'Klamath' and are sold as
the Pentium II versions 233 up to 300 MHz. It has got four second level
cache modules with the speed marking of 7 ns. Due to the fact that it's only
rated for speeds up to 150 MHz (300 MHz/2), the Klamath's second level
cache timing is the fastest of all Pentium II CPUs, giving it a performance
edge compared to Deschutes CPUs at the same clock speed, which of course

                                        A GUIDE FOR OVERCLOCKING / 19
is academical, since Deschutes starts at 333 MHz in a Pentium II. The
Klamath core is larger than the core of the Deschutes, because it's still
manufactured in .35 micron technology. This is also responsible for the larger
heat production of the Klamath, compared to the Deschutes core. The
common core voltage requirement of the Klamath is 2.8 V.

Many or most of the Klamath CPU's have the multiplier restricted, so
that you cannot exceed the allowed core frequency as long as the front
side bus frequency stays unchanged. Some 266 MHz CPUs can run at
300/66 however, so that some people specialized in counterfeiting the plastic
package of a Pentium II 266, selling them as Pentium II 300 CPUs. Usually
Pentium II 233 and 266 CPUs come without second level cache ECC and
Pentium II 300 are pretty much all sold as second level cache ECC version.
Thus c't-Magazine is asking every owner of a Pentium II 300 to check if their
CPU is supplied with ECC level 2 cache, using a little program you can
download from their website. If you have got a Pentium II 300 without ECC L2
cache you have most likely got a counterfeit Pentium II 266.
The Klamath is certainly overclockable, but in most cases it requires the
increase of the front side bus frequency (external bus speed), which is
dangerous for your PCI and AGP devices, because they run at PCI/AGP
clocks above spec. Some crazy people overclock Pentium II 300 CPUs up to
375 MHz and even more. This is certainly an interesting thing to do, alas it is
pretty useless for anyone who needs a reliable system. As a overclocker
you've got to live with the fact that your system can crash any time. The L2
cache, in a Pentium II running at half of the core clock frequency and
rated at 7 ns is absolutely not designed for clock speeds exceeding 150
MHz, maybe it will do 166 MHz in some cases, but don't expect any reliability
of a 7 ns L2 cache running at 175 MHz or even more.

Intel Pentium II 333 - 400, Core Codename Deschutes

Intel managed shrinking the core of their 6th generation MMX CPU to 0.25
after the Klamath was on the market for roughly 8 months. This resulted in
higher core frequencies, lower voltage requirements and less heat production.
However, higher core speeds mean higher second level speeds as well, so
that Intel needed to change the modules for the second level cache as well as
its timing. The new L2 cache modules are packed at a higher density, so that
only two modules are required. These new modules are rated 5.5 ns for 333
and 350 MHz Pentium II CPUs and 5 ns for 400 MHz Pentium II CPUs.

The new generation of Pentium II CPUs is now running at 100 MHz front side
bus, whilst the Klamath as well as the Deschutes at 333 MHz are only
supposed to run at 66 MHz FSB. Intel's BX chipset is able to recognize which
kind of CPU is plugged into the motherboard, so that most BX motherboards
are following the Intel spec and supply the correct front side bus frequency

                                         A GUIDE FOR OVERCLOCKING / 20
There is a serious difference between 333 and 350 MHz Pentium II CPUs and
its brother at 400 MHz and above. The 400 MHz version has got faster L2
cache modules. Another major difference is the timing of the L2 cache. The
L2 cache timing of the Pentium II 233-300 MHz CPUs is faster than the L2
cache timing of the Pentium II 333. Now the timing of the 5 ns L2 cache in the
Pentium II 400 is even slower than in the 333 and 350 models. This is
something that should be considered by hardware testers that want to use the
easily overclockable Pentium II 333 as test CPU for 400 MHz testing,
because the benchmark results scored by this overclocked CPU are higher
than what you would get with a real 400 MHz Pentium II.

Overclocking of Pentium II with Deschutes CPUs will in most cases also
require the increase of the front side bus, since the higher multipliers will
mostly be disabled by Intel. The Pentium II 333 has a multiplier up to 5x built
in, so that you can theoretically reach pretty high clock rates, as long as a BX
motherboard will let you run this CPU at 100 MHz FSB or even more.
Motherboards that detect the FSB clock automatically can only be fooled if
you should be courageous enough and change the above mentioned resistors
on your CPU PCB. I recommend you rather go for a motherboard that let's
you choose 100 MHz FSB or more regardless what CPU is in there.
Overclocking is pretty dangerous when you look at the system stability point
of view. The CPU core will in most cases do the higher clock rate just fine,
however the L2 cache running at half of this higher clock speed will most
likely cause erratic behavior and can easily be the reason for system crashes.
The Level 2 cache, which operates at approximately one half the speed of the
CPU, is matched by Intel to the speed of the CPU core to which it is
connected. There's usually a good deal of leeway, but the individual speed of
your cache is a key limiting factor in overclocking your CPU. AAH!!!

I consider everyone as really irresponsible, who runs his business software on
a system with a highly overclocked CPU. Nevertheless, keeping in mind that
you can run into system crashes at any time, overclocking works pretty well in
the following cases:

Pentium II 333 :- 350/100 3.5 inner multiplier and 100 MHz FSB (requires
motherboard that let's you choose 100 MHz FSB)
Pentium II 350 :- 392/112, possible L2 cache issue, possible PC100
SDRAM issue at 112 MHz
Pentium II 400 to 448/112, possible L2 cache issue, possible PC100
SDRAM issue at 112 MHz
People that overclock to more than that either post this to make themselves
look important without using the system at this speed. Reaching higher
speeds safely only works with special 7 ns SDRAM modules and a special
cooling system.

Intel Celeron, Core Codename Deschutes

                                          A GUIDE FOR OVERCLOCKING / 21
The Celeron, Intel's attack on the CPU suppliers of the low end market,
comes with the same 0.25 micron core as the Deschutes and is therefore
'more modern' than the Pentium II 233-300 CPUs with their 0.35 micron
Klamath core. Celeron has not got any L2 cache and is otherwise identical to
the other Pentium II CPUs. Thus is can show its strengths when running
floating point calculation intensive applications like 3D games in the first
instance, a field where it is faster than any currently available socket 7 CPU.
The lack of L2 cache results in a decent but not amazing office application
performance, but it has got it's advantages as well. As you learned from the
stuff above, the L2 cache is making the most trouble when clocking the Slot 1
CPUs higher. The Celeron doesn't have to worry about that. Only newer
successor have an internal L2 cache and hence will be more sensitive to
higher clock speeds as well. This leads to the simple conclusion that only the
core is responsible for the success in overclocking the Celeron. Now the
sweet thing about the Celeron is the fact that it's using the Deschutes core, as
already mentioned. This core was designed to run at least 333 MHz as in the
Pentium II 333. The 0.35 micron Klamath is already reaching 300 MHz
without a problem, so that you can imagine that you will hardly find a
Deschutes core that doesn't at least do 333. These cores are used in a
Celeron and the Celeron is specified to 266 MHz only to not damage the
sales of the Pentium II 233, not because the core wouldn't be fast enough. So
here we are, Celeron is the number one overclocking CPU and if you should
run it fast enough, you can even reach Pentium II 350 scores, particularly in
3D games as Quake II, but by paying less than a third for it. The problem for
overclocking is that you will need a BX board that doesn't detect the FSB
clock automatically, so that you can run this baby at 100 MHz FSB.

The Celeron comes !! naked !! as Intel created it. No plastic cartridge covers
the PCB and the heatsink that comes with it has to be fixed in a slightly
annoying procedure. Intel was trying at least a little to keep people from
plugging Celeron into LX or BX boards. The little mounting brackets which fit
nicely in any EX board wouldn't fit at all into LX or BX boards. Until then you
shouldn't play cricket with your computer after plugging the Celeron in your LX
or BX board, because you won't be able to secure the Celeron in Slot 1. This
is important for people in earth quake endangered areas.
There isn't much more than the CPU core on the PCB of Celeron. Please note
that you won't find the R5/R6 resistors as in Deschutes for allowing it 100
MHz FSB officially. The Celeron is meant to be running at 66 MHz FSB only

The goal of overclocking is to find your CPU's comfort zone--the speed at
which it will run reliably, without system errors or data corruption. Here are
some common, relatively conservative settings.
Pentium IIs With Default 66 MHz FSB (233 MHz to 333 MHz)

                                          A GUIDE FOR OVERCLOCKING / 22
        233-MHz and 266-MHz Pentium IIs
          Overclocked Speed Clock Multiplier FSB Speed Chipset
          300 MHz             4.0             75 MHz      440LX
          300 MHz             3.0             100 MHz     440BX
          336 MHz             3.0             112 MHz     440BX

        300-MHz Pentium II
          Overclocked Speed Clock Multiplier FSB Speed Chipset
          338 MHz             4.5             75 MHz      440LX
          350 MHz             3.5             100 MHz     440BX
          392 MHz             3.5             112 MHz     440BX
          400 MHz             4.0             100 MHz     440BX

        333-MHz Pentium II
          Overclocked Speed Clock Multiplier FSB Speed Chipset
          350 MHz             3.5             100 MHz     440BX
          375 MHz             5.0             75 MHz      440BX
          392 MHz             3.5             112 MHz     440BX
          400 MHz             4.0             100 MHz     440BX

Note: To run reliably at a 100-MHz FSB, you need to have 100-MHz SDRAM
installed in your system. Also note that in many of the cases listed above,
increasing the FSB speed requires you to lower the clock multiplier on your

Pentium IIs With Default 100-MHz FSB (350 MHz to 450 MHz) Since
August 1998, Intel has been locking the clock multiplier on its CPUs, so
it probably will not be possible to change the multiplier when
overclocking a 350-MHz, 400-MHz, or 450-MHz Pentium II. If you try, the
CPU will either refuse to boot the machine, or it will boot it up at 1/3 its
proper speed. To get around this limitation, a Pentium II overclocker's
only remaining option is to increase the speed of the frontside bus.

350 MHz (and above) Pentium II
                                                Overclocked Overclocked
Default Clock Speed Default Clock Multiplier
                                                FSB Speed CPU Speed
350 MHz               3.5x                      112 MHz       392 MHz
400 MHz               4x                        112 MHz       448 MHz
450 MHz               4.5x                      112 MHz       504 MHz

                                        A GUIDE FOR OVERCLOCKING / 23
Overclocking Step by Step

1.   Turn off computer, open it up, get your motherboard manual.
2.   Check your CPU markings on top and bottom of CPU, write them down
     and put your CPU back in again.
3.   Check the current clock speed and multiplier jumper settings on our
     motherboard, compare them with your manual, write them down.
4.   Check the supply voltage jumper settings on your motherboard, compare
     them with manual and your CPU marking, write it down.
5.   Have you thought of a decent cooling for your CPU ? Apply it !
6.   Change the jumper settings for clock speed and/or multiplier according to
     your manual.
7.   Check if everything is ok, no jumper forgotten or put wrongly.
8.   Start computer.
9.   Does it reach BIOS setup ?
10. If yes, go to 13.
11. Turn off computer and change jumper to higher supply voltage according
    to manual, if possible.
12. If you still shouldn't reach BIOS setup, forget about overclocking to this
13. Change BIOS setup settings to the right values.
14. Does it reach full working operation system ?
15. If yes, start testing (I recommend Winstone or the BAPCo Suite. Don't
    take this job too easily! It's better to occur crashes or lock ups now, than
    coming across them when it counts!)
16. If no, you should try 11 or check your cooling, you also can try some
    more conservative memory timings in the BIOS setup. This means
    increasing the wait states or the read/write cycles; but don't forget to
    check later if you gained speed by trying some benchmarks, cause
    there's no point in overclocking if your memory access is getting slower.
17. If everything works well – congratulations !!, if not, try 11, check cooling.

18. Don't change supply voltage unless you have to. It only makes the chip
19. Never forget: cooling is of main importance !
20. Reread following Prelaunch Checklist.

                                           A GUIDE FOR OVERCLOCKING / 24
Simple Flow Chart Steps for OVERCLOCKING

IN THE END - A little about me.

Hi my name is Shrishail Rana.

I am currently doing my post graduation in law and yes computers are my
hobby, love or whatever you can say.

If you have any questions please send an email at srana4u@hotmail.com.

Bye for now. Wait and watch for              more    on   my   web       site

Please also visit www.tomshardware.com for more information because most
of the guide is written with help from Tom's site.


Disetting Ulang Oleh
Indung Widya I.

                                       A GUIDE FOR OVERCLOCKING / 25

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