Reply 20 of 41, by vetz
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- l33t
wrote:SCSI was quirky in terms of drivers and compatibility with the various devices before ASPI, but it was almost always a slow drive to blame if the drivers and software were correct. I never saw any IDE system back in the day that could touch a properly set up SCSI system in terms of CPU usage--it was that much of a difference.
And I think you may have the bottleneck backwards as Fast SCSI could transfer 10MB/sec while the ISA bus maxed out at 8MB/sec. If anything, the SCSI drive would have to wait on the bus and cpu.
When I did alot of benchmarks on controllers (mainly VLB, but also ISA) between IDE and SCSI for this thread I noticed that with newer drives IDE wins over SCSI on an older system. Granted, most of it was on VLB, but I still think it holds up even on ISA as a PIO MODE 2 VLB controller had almost the same performance as an ISA IDE controller. A newer SCSI and IDE drive on a ISA bus will most likely max out both bus speeds, so it will come down to cahce and seek times on the drives. You also have to remember that for DOS, SCSI is hampered from the start due to the overhead on SCSI controllers since they need to translate between SCSI commands and DOS int13, while IDE doesn't need to do this. DOS doesnt take advantage of the special SCSI features like command queuing like a proper operating system does. As you say, with the right controller and a supported operating system SCSI was better and faster back in the days.