MicroVax II

Steven M Jones classiccmp at crash.com
Tue Aug 2 22:27:35 CDT 2016

On 08/02/2016 19:49, Douglas Taylor wrote:
> I had 3 different types of SCSI CDROM's and none of them worked [...]
> Is there a SCSI CDROM to look for?

That's unfortunate. The DEC badged drives would be ideal, but you should
be good with Sun-, HP- or SGI-badged drives, or Plextor and Toshiba
drives with a SCSI interface. For the non-workstation vendors, search up
the model spec sheets to see if you need to change a jumper or, in
unusual cases, cut a trace on the PCB.

All this info can be found on (third-party) CD-ROM FAQs for the
workstation vendors...

> I'm curious about the 68 pin scsi drives, what type do you use?  The
> adapter, I guess it is 50 pin male to 68 pin male?

The 68/80 to 50 pin adapters are straightforward and all over eBay. Be
advised that some drives spec'd for Ultra 320 may need a jumper or
simply won't behave properly on an 8-bit SCSI bus, but its doesn't seem
to be that common.

If you're looking for spinning iron, I'd recommend drives using the 80
pin SCA connectors. Checking the labels is best, but as a rule of thumb
they tend to be more recent production. However all of them are getting
long in the tooth!

For physical drives, most recently I've been getting the 2.5" Seagate
Savvio drives with the SCA connectors. They tend to "only" be ~10 years
old, and the smaller form factor often makes it easier to squeeze them
and the coverter board into drive carriers designed for 3.5" devices.

Be aware that if you don't know your equipment uses High Voltage
Differential (HVD) SCSI, avoid it or things that just say
"Differential." It will fry older/slower and Low Voltage Differential
(LVD) SCSI gear.

Sorry if any/all of that was already known, but I'm avoiding actual work
this evening. ;)


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