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Lesson 38
12/5/08

Learn about memory on the motherboards
Learn about different types of RAM

Mini Lesson

RIMM Technologies – Direct Rambus DRAM or RDRAM or Direct RDRAM or Rambus is
named after Rambus Inc. the company that developed it. RDRAM uses RIMM memory modules.
Rambus designed the technology but does not actually manufacture RIMMs. Because
manufacturers must pay licensing fees to use RDRAM the industry has turned more to SDRAM
memory advancement.




Error Checking and Parity

      Parity
           o Error-checking procedure in which every byte has an even number of ones or an
              odd number of ones
           o Older method of testing integrity of bits
                   Stored in RAM or secondary medium
                   Sent over a communications device
      Error-correcting code (ECC)
           o Current method of error checking that can detect and correct an error in a single
              bit
Parity




Other Memory Features

            CAS (column access strobe) latency
            RAS (row access strobe) latency
            Both CAS and RAS refer to the number of clock cycles it takes to write or read a
             column or row of data


Memory Speeds: Factors to Consider

            Speed of memory in ns, MHz, or PC rating – use the fastest memory th motherboard
             supports
            How much memory is installed – the more memory there is, the faster the system
            Memory technology used – DDR is faster that SDR SDRAM
            CL rating – the lower the better
            ECC/parity or non-ECC/nonparity – non-ECC or nonparity is faster

Factors That Contribute to Memory Speed




Upgrading Memory

            What to look for when buying memory chips and modules
            How much and what kind of memory to buy
          Reading ads about memory modules
          Installing memory


What to Look for When Buying Memory Chips and Modules

      Use type, size, density, and fastest speed supported by the motherboard
      Match tin leads to tin connectors and gold leads to gold connectors
      Beware of remanufactured and re-marked memory chips

How Much and What Kind of Memory to Buy

      Determine how much memory you have and need
      Identify the number, type, and size of memory modules supported by your motherboard
      Determine how much memory can you afford
      Match memory modules to the motherboard


Review


Why are the memory manufacturers turning to SDRAM instead of RDRAM?
What is parity?
What is ECC?
What are CAS and RAS?
What factors contribute to the memory speed of a computer?

				
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