On 01/23/2018 10:33 AM, Jack Harper via cctalk wrote: It's a toasty 20F here in northern MN :) 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? 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

What SCSI controller are you using - MVME320, 327 or 328 ? Do you reset the MVME177 board using RESET command from 177bug> along with SCSI bus reset option? Best regards, Plamen On Tue, Jan 23, 2018 at 6:33 PM, Jack Harper via cctalk < cctalk at classiccmp.org> wrote: