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[ The PC Guide | Systems and Components Reference Guide | CD-ROM Drives | CD-ROM Performance and Reliability ]

Processor Utilization

A performance consideration that most people don't think about very much is the impact of CD-ROM transfers on the rest of the PC. This is a factor that is based a great deal on the interface that is used by the CD-ROM drive. While both SCSI and IDE/ATAPI are acceptable interfaces for CD-ROM drives in terms of their capability for dealing with the transfer rates required by the drives, there is a big difference between the two related to how much demand they put on the system processor.

As described in detail here, the ATAPI protocol is used to connect CD-ROM drives over the standard IDE interface that was once used only for hard disks. Using this interface, however, requires substantial involvement by the processor to perform transfers. When the CD-ROM is being accessed, much of the processor's time will be unavailable to do other work. This is not the case with SCSI.

In the real world, the importance of this distinction depends, as always, on how you are using your PC. For the typical home user who is doing one thing at a time, there will probably not be much difference noticeable at all. For someone doing a lot of CD-ROM accesses in a multitasking environment, or sharing CD-ROM drives over a network, SCSI is almost always the way to go. See this comparison of SCSI and IDE.

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