DEC VS2000 and SCSI, was Re: DEC RD54 from Maxtor

From: Steve Jones <classiccmp_at_crash.com>
Date: Wed Mar 5 12:52:00 2003

John Allain writes:
.
> Somebody should say here that it's pretty strange to have a
> workstation that has all SCSI connectors on the outside and
> an MFM disk on the inside. I did a mental doubletake on this
> ("hey, this makes no sence") a short while ago.

Since I haven't seen any other responses, I'll dive in... This is
all speculation - I'd love to have someone with a line into DEC
Engineering answer this properly. To put it another way, I may be
completely off my rocker - reader beware! ;^)

The VAXstation/MicroVAX 2000 was released in 1985 (cf. R.D. Davis'
uVAX FAQ), which means development and planning may have started
as early as 1983 - I'm just guessing here.

In the early 80s large (> 20MB) ST-506 hard drives were still
hugely expensive beasts. If you did find a native SCSI device, I
imagine the costs would be much higher for the extra interface logic
on the drive. Without native SCSI on the device, you needed a
translator like the Adaptec ACB-4000 (SCSI/ST-506) or Emulex MT-02
(SCSI/QIC-02).

The base VS2000 was a pretty small box - perhaps even ground-
breaking for this timeframe, given it could run full 32-bit uVMS
or Ultrix and had internal storage, unlike the Sun-2/50. Having to
develop and wedge in a unique converter board may have been riskier
than adapting a version of a board you were already producing/
designing for the other uVAX models like the RQDX3.

Going back to that comparison to the Sun-2/50 may answer the question
of why SCSI was acceptable for the tape interface. Since the tape
drive was going to be external, there's plenty of room for that extra
logic board. And it's only a tape drive, so if we can't get decent
throughput out of our first (?) SCSI interface, well, who's going to
notice when the tape drive is as slow as the TK50? ;^)

After a few years of Apple, Sun, and others driving SCSI into the
marketplace the whole picture changed and by the time the first pizza
box workstations come out everything is SCSI.

Anyway, that's my best shot at an explanation. Again, I'd love to
hear from someone who was inside DEC (Megan?)...

--Steve.
Received on Wed Mar 05 2003 - 12:52:00 GMT