On 19 Jan 99, at 16:45, Changhsu Liu wrote:

> Are there speed limits on different SCSI cables (e.g., DB68, DB50,
> centronic 50)? I have a ultra-wide scsi card but I don't have any
> DB68 cable or ultra-wide scsi HD. I bought a converter to convert
> db68 to db50 scsi cable. Just wonder if using converter would make
> the scsi slower than using its own scsi cable. Maybe it does not
> matter since my drive is not ultra-wide anyway.

  The preferred option is to do any 68-50 conversion at each drive,
rather than at the controller.  That way, the 18 additional lines can
be terminated at the same point as all the others, and this is strongly
recommended.

> Let me ask in another way if my question is unclear. Compare
> scenario 1 with scenario 2 below, will scenario 1 HD run slower than
> scenario 2 because it has to go thru conversion?
>
> <=> means connection
>
> 1) Ultra-wide SCSI Card <=> SCSI converter (from 68pin to 50pin) <=>
> 50pin SCSI cable <=> SCSI converter (from 68pin to 50pin) <=>
> external ultra-wide SCSI HD
>
> 2) SCSI Card <=> 68pin SCSI cable <=> external ultra-wide SCSI HD

  If you can get #1 to work at all (and I have a couple of reasons for
believing that this will be difficult), it will provide less bandwidth
than #2.  It would probably provide more bandwidth than the drive can
actually USE, so the cable wouldn't actually be the bottleneck.


David G

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