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PREFACE:
The Small Computer System Interface (SCSI) standard is
a very large topic. I have enjoyed SCSI devices and highly recommend
them. SCSI provides several advantages over IDE. However, three
major disadvantages to SCSI are price, heat dissipation, and complexity.
SCSI has continued to evolve from SCSI 1 to SCSI 2 to
SCSI 2 WIDE to SCSI 3 to SCSI 3 WIDE to ultra SCSI to ultra2 SCSI, and to 160M
or 320.
ADVANTAGES:
SCSI allows for both internal devices like hard drives
and CD drives as well as external devices like scanners and cameras. IDE does
not.
SCSI allows up to seven devices and ultra SCSI allows
up to 15 devices per controller. IDE allows 2 per controller.
IDE and SCSI have been evolving and competing for
years on performance. This competition is now a meaningless numbers hype
game. Look at EIDE Ultra DMA/66. It's supposed to provide for 66MB/s
throughput. The Ultra2 SCSI is supposed to provide for 80MB/s
throughput. Both sound impressive don't they? These are maximum
theoretical/burst rates and have nothing to do with reality. It's a matter
of hard drive technology (magnetic media and pick-up heads) and platter
rotational velocity. The main difference is in the drive controller
technology.
I have an Ultra DMA 66 EIDE drive and an Ultra2 SCSI
drive. Neither drive provides anything close to the maximum
theoretical/burst rates. The Ultra2 SCSI drive picks right up and steadily
cranks out an 18MB/s throughput rate. It is rock solid. And it is
exactly as the manufacturer advertised. The DMA/66 drive cranks out 13MB/s
but fluctuates wildly. Take it from me, SCSI is faster and has a higher
sustained consistent throughput rate. Also, there are Audio/Video (A/V)
SCSI drives. Professional A/V work requires high, sustained, and
consistent throughput bandwidth. You won't find an IDE A/V drive.
PRICE:
HEAT DISSIPATION:
COMPLEXITY:
The device ID has to be assigned a different ID using
jumpers or by SCSI Configured Auto Magically (SCAM).
The cable has to be terminated at each end. So
remember to set the terminator resistors on the SCSI controller and the last
device in the SCSI chain. The SCSI "chain" is the controller, cable,
and all devices sequentially connected to the cable. The cable can only be so
long. SCSI performance continues to evolve with IDE, one will get a leg up on
the other and vice versa. I have had SCSI and have really enjoyed it, they seem
to move continuous blocks of data faster than the corresponding IDE and you can
get some very large hard drives with small access times. SCSI is, however, more
expensive, both adapters and hard drives. | 