Great information/advice Jules.
I appreciate it - and know more about SCSI now than before.
Regards,
Jack
At 11:15 AM 1/23/2018, Jules Richardson via cctalk wrote:
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
correct.
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 causes glitches)
*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.
cheers
Jules
----------------------------------------------------------------------------------
Jack Harper, President
Secure Outcomes Inc
2942 Evergreen Parkway, Suite 300
Evergreen, Colorado 80439 USA
303.670.8375
303.670.3750 (fax)
http://www.secureoutcomes.net for Product Info.
