SCSI Controller Hanging...
jules.richardson99 at gmail.com
Tue Jan 23 12:15:03 CST 2018
On 01/23/2018 10:33 AM, Jack Harper via cctalk wrote:
> Greetings to the List from the Snowy Rocky Mountains.
> Beautiful clear sunny day here at +9F :)
It's a toasty 20F here in northern MN :)
> I have never before dealt with SCSI as a programmer - does this sound like
> something is configured incorrectly?
> There is not much to configure.
I'm not sure about incorrect config, but I'm guessing it could be a
software issue (rather than hardware) - i.e. board reset is also causing a
reset of the SCSI bus in some odd way which is then offlining/confusing any
attached devices. Does it just happen with a reset of one specific CPU
board, or is it any of them?
> I point out that I am not certain that I have the termination resistors
Termination's easy enough - in theory :-) A single set of termination at
each end of the bus, never in the middle - and double-termination at either
end will cause weird things to happen.
If it's a 16-bit SCSI bus then you need termination either end of both
high/low 'halves' (sometimes people will park an 8-bit device via a cable
adapter at the end of a 16-bit bus, and stick an 8-bit terminator on the
device, which leaves the high side of the 16 bit bus unterminated and
*Something* on the bus needs to provide +5V on the SCSI TERMPWR line; the
terminators need this to work. I think typically the bus adapter (i.e.
controller) will do this, but I seem to recall that the adapter in my Apple
IIGS has no support for it and expects one of the attached devices to do it
(some will via a jumper setting, but some won't)
I think that some 16-bit devices will automagically work on an 8-bit SCSI
bus, but I don't know if there's any guarantee of that.
Other than that, if you've got external devices then try and use the best
quality cables that you can find - there used to be some really cheap junk
out there which could cause all sorts of oddball problems.
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