[Wylug-help] SCSI Parity

[James Holden (Wylug)]

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Graham Whaley wrote:
| James,
|   I don't know about turning the parity off, but something to watch
out for
| is cable lengths.  As the SCSI frequency ramps up (5/10/20 Mhz), the
maximum
| cable lengths (for the whole chain) drops.  So, on your O2, which runs
20Mhz
| Ultra wide SCSI I think, the maximum cable length is 1 Metre.  That is for
| all devices added up on a single chain.  I had to hand build a 500cm cable
| to get an external Ultra wide drive to work on an O2.  Interestingly, the
| errors I saw included parity errors.  Problems only turned up when we were
| 'hammering' the O2's drive.  It booted and ran fine until we tried to do a
| major compile.
|
|   Just something to be aware of if you are plugging a old and slow device
| (5Mhz, standard SCSI-1) into a faster machine.
|
|   If you really need some more info then I have the official SCSI-2 spec
| laying around here somewhere.
|
|   While we are here, anybody want some old 2Gig SCSI drives?  Might have a
| set of 4 matching ones if anybody wants a 6/8 gig raid.  Otherwise
they will
| get scrapped one day.
|
| 	Graham

[snip]

Actually, the problem is worse on the O2. The printer won't power on
when it's connected to it. I used a 60cm cable, and the external
interface on the O2 normally has an 80GB IDE drive attached to it, so I
know there's no issues with wide/narrow/fast/slow/cable length etc...

The usenet thread seemed to match my problem, though. I'm convinced
that's the problem at present.

Are the 2GB drives half-height or 1" profile?

James
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