Answers by gegeshandong


									Chapter 12 Solutions                 -       Corrected

Answers to Key Term Quiz
1. In addition to being limited to no more than 6 meters, SCSI-1 chains frequently had
   incompatible devices, especially if they were purchased from different vendors. Page 397

2. The most commonly used internal cable for Wide SCSI-2 is the 68-pin ribbon cable.
   Page 402, also page 392.

3. Termination prevents the signal from reflecting back up the wire. Page 395

4. Mark needs to use a 50-pin high density (HD) connector to connect his narrow SCSI-2
   printer to his host adapter.      Page 402 (Note that a printer is an external device).

5. A SCSI chain consists of the SCSI host adapter and all internal and/or external devices.
   Page 391

6. Forced perfect termination (FPT) uses diodes and polarity to block backward current
   flow more effectively than resistors.     Page 401

7. Each SCSI device, including the host adapter, must have a unique SCSI ID. Page 393

8. The terms Ultra, Ultra 2, and Ultra 3, operating at 20, 40, and 80 MHz respectively, are
   used to define high-speed SCSI-3 buses. Page 399

9. Daisy-chaining describes the action of attaching one external SCSI device to another
   directly.   Page 393

10. John should use a 68-pin high density (HD) connector to connect his SCSI-3 scanner to
   his host adapter. Page 402
Answers to Multiple Choice Quiz
1. A. (The default SCSI ID for a bootable SCSI drive is 0.)          Page 395

2. A. (All the following describe correctly terminated SCSI chains except “With both
   internal and external devices, terminate the host adapter, the last internal device, and the
   last external device.” SCSI terminates only the ends of the chain, so the host adapter in
   the middle should not be terminated.)      Page 395, see Figure 12.15

3. B. (If you attach the ribbon cable backward so that pin 1 on the cable does not align with
   pin 1 on the SCSI device, likely the device will not work and will probably be destroyed.)
   Page 392

4. D. (All the following statements are true about the SCSI-2 standard except fast SCSI is
   serial whereas normal SCSI is parallel.) Page 397 & 398

5. A. (The maximum length of a SCSI-2 chain composed of HVD devices is 25 meters
   while LVD chains are limited to 12 meters.)       Page 399

6. D. (If you just installed a SCSI device and the host adapter does not list the device when
   it initializes, all of the above may cause the problem.)   Page 404

7. C. (By using LUNs, you can attach up to seven devices to a single SCSI ID.) Page 396

8. B. (All the following statements correctly identify SCSI cables except “Type B is a 40-
   wire cable that is rarely used.” EIDE, not SCSI, uses a 40-wire cable. The rarely used
   Type B cable contains 68 pins and must be used with the 50-wire cable.) Page 402

9. A. (The true statement about mixing IDE and SCSI devices on the same computer is “The
   IDE drives will get a drive letter before the SCSI drives unless you configure the BIOS to
   boot to SCSI before IDE.”)         Page 403

10. C. (All the following are advantages of using SCSI rather than EIDE devices except
   “SCSI devices are less expensive than EIDE devices.” Actually, both the SCSI host
     adapter and SCSI devices are more expensive than their corresponding EIDE
     counterparts.)    Various pages, chapters 9 (hard drives) and 12 (SCSI drives)

11. C. (You can obtain the best speed and performance if your host adapter fits the PCI bus.)
     Page 391, also page 402

12. B. (The true statement is “Various flavors of SCSI devices attached to the same host
     adapter communicate at the maximum speed supported by each device.” The exception is
     a SCSI chain that mixes LVD and SE devices attached to the same host adapter, in which
     case, the whole chain runs at the speed of the slow SE device.) Pages 402 & 403

13. C. (If the jumper block on the SCSI device contains four jumpers identified as 1, 2, 3, and
     4, covering jumper 2 and 3 but leaving jumper 1 and 4 open would assign SCSI ID 6 to
     the device. Using binary math, jumper 1 has a value of 1; jumper 2 has a value of 2;
     jumper 3 has a value of 4, and jumper 4 has a value of 8. Covering jumpers 2 and 3 then
     combines the values 2 + 4 for ID 6.)     Page 394

14. A. (The statement that best describes bus mastering with SCSI devices is “If SCSI
     devices are on the same SCSI host adapter, they can communicate directly with each
     other without the assistance of the CPU or the use of the expansion bus.”) Page 401

15. C. (After the SCSI hard drive has been installed correctly, you partition and format it
     exactly the same way that you do an EIDE drive.)        Page 403

Answers to Essay Quiz
1.      The main points here are the larger number of devices that SCSI supports from a
single host adapter and the ability to daisy-chain external devices. Other points might include
the stability and speed of SCSI devices. Obviously, SCSI-3 with its hot swap capability and
increased transfer speed would be the flavor choice.
2.     SCSI drives are not configured through CMOS setup. Instead, the host adapter with
device drivers controls everything on the SCSI chain. While some setup programs include a
SCSI selection, it does nothing except prevent people like Barbara who are not familiar with
SCSI technology from wondering how a drive can work without configuration. Another
CMOS setting that may affect SCSI is the boot sequence that will enable a SCSI drive to
serve as the boot drive and will usually assign it a drive letters before the IDE drives. In case
of possible resource conflicts, you can use CMOS to view resource assignments. If the
computer displays a “HDD failure error,” it may mean that it is looking for a nonexistent IDE
hard drive. Go to CMOS and indicate that you have no IDE drive.

3.     By providing greater storage area through more drives, both internal and external,
SCSI is particularly good for network servers and for high-powered multitasking applications
such as CAD. The bus mastering capabilities of SCSI leave the CPU free to handle other
tasks. In addition to providing up to 15 devices from a single host adapter, SCSI is faster with
better data throughput than EIDE. The firm might also benefit from devices such as a SCSI
scanner or tape-backup device.

4.     Regardless of the SCSI configuration, there will be only two terminators, one at each
end of the chain. All devices between these two will have termination turned off, including
the host adapter when both internal and external devices are used on the same chain. As for
SCSI ID numbers, the host adapter defaults to ID 7 and should not be changed. Any other
numbers (within the range of the SCSI flavor) are acceptable and numbers do not need to be

5.     SCSI devices use a Molex connector for power supply. The ribbon cable runs
between the controller and the device, with the red stripe on the cable oriented to pin 1 on
both devices. Multiple internal devices can be connected together simply by using a cable
with enough connectors. While connecting a number of devices on the same SCSI chain, you
must provide some way for the host adapter to tell one device from another. To differentiate
devices, SCSI uses a unique identifier called the SCSI ID. The SCSI ID number can range
from 0 to 15. All SCSI drives use simple binary to set the ID. In all jumper instances, when
setting SCSI IDs, use the value of the jumpers in binary: the first jumper has a value of 1, the
second has a value of 2, the third has a value of 4, and the fourth has a value of 8.

The rule with SCSI is that you must terminate only the ends of the SCSI chain. You have to
terminate the ends of the cable, which usually means that you need to terminate the two
devices at the ends of the cable. Do not terminate devices that are not on the ends of the
cable. Improper termination can cause damage to SCSI hard drives.

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