RE: tlug: Fast/Ultra SCSI compatibility

[Thomas Bätzler <tbaetzle@example.com>]

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tlug note from =?iso-8859-1?Q?Thomas_B=E4tzler?= <tbaetzle@example.com>
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>tlug note from "Francis Brian O'Carroll" <ocarroll@example.com>

>>If I have an ultra scsi interface can I attatch fast scsi peripherals to it?

Sure, no problem - the host adapter negotiates transfer speed and
options 
with each attached target in the initialisation phase. 

>>If so, and the scsi bus has both a new ultra scsi disk and an old
>>fast scsi disk, say, does the slower device slow down all other devices
>>on the same scsi bus?

Only in so far that the slower device just ties up the bus a bit longer
when 
it's doing transfers. Unless you have a real high-end system that should
not be an issue at all, since the bandwith is usually not limited by the
bus speed, but by the hardware that uses it. Well, aren't we all glad
that
SCSI is a bit more sophisticated than the IDE master/slave concept?

>>And what about wide scsi vs normal scsi. I know that there are different
>>numbers of pins on the cables, but can normal scsi devices be attatched
>>to wide scsi or ultra wide scsi interfaces, and if so, is there any
>>downside to doing so?

I'm not too sure about mixing wide and normal SCSI, but normal/ultra and
normal/fast work fine. In my system, I have two IBM DORS (fast SCSI HD)
aswell as a Toshiba TM5401 CDROM drive hooked up to an Adaptec 2940U
host adapter. Linux tells me it talks at 10MB/s with the HDs, but only
with
3MB/s with the CDROM. Still I get the usual 4-5MB/s on reads from the
HD.

HTH,
Thomas

PS: Since I'm already posting to the list, could anybody tell me where
the
list archives are currently kept? I'd like to browse them from
information on
configuring the JE stuff before I start asking FAQs. Alta Vista told me
that
they were in http://bbg.twics.com/~craig/list_archive, but they aren't
anymore. Thanks!

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