MicroVAX 3100 questions

From: Fred N. van Kempen <waltje_at_pdp11.nl>
Date: Sun Aug 10 13:39:01 2003

Chris,

Late reply... was kinda busy.

> I've become the new owner of a nice MicroVAX 3100, and I'm trying to learn
> more about it. I had a few hardware-related questions, and I'm hoping that
> someone here can give me some insight.
Yay! The 3100, albeit a bit slowish, are nice boxes... they're a real
VAX, they use SCSI for I/O (read: cheapo drives and stuff) and, as long
as they're taken care of, virtually indestructible. I have about 30 of
them :)

> This is what I know about the system so far -- it's got three RZ26 drives
> in it, although one appears to have died, since SHOW DEV only reports two
> installed. If I were to replace the failed one, do I need to get my hands
> on another Digital drive, or will any SCSI drive work with VMS? Also, I've
> heard that some vaxes (or was it VMS, or both?) have limits on the size of
> the drive it will work with...what would work best in this system?
The 3100 will not be able to boot off drives larger than 4GB, because of
how their ROMs address the sectors. Once booted, the OS takes over, and
they have no real limits. So.. make sure the OS boot area "lives" below
that size, and you're fine. Very old ROMs have a 1GB limit, but rather
than going with those, just swap the ROMs :)

Also, DEC drives are good, but any good SCSI drive will do. Many people,
me included, use Seagate HAWK drives (2GB, 3.5", 1" low-power), which now
come dirt-cheap.

> My VAX came with VMS 5.5-2 installed, but I'd like to go ahead and get the
> hobbyist license and move to 7.2. Will my little VAX handle it? It's got
> 16 megs of memory and about 2 gigs of hard disk space (unless I can coax
> that other RZ26 into working...)
16MB is pushing the limits for 7.x. I believe it *does* run, but it will
be slow as hell, and probably slower than that :) Try to stick to 5.5 or
6.x, or find more memory. The machines has a 32MB limit, by the way.

> Also, I don't have a CDROM, or a place to put it in the case. Again, if
> I get an external SCSI case, does it or the CDROM I put in it need to be
> specific to the VAX?
External cases work find (it IS just regular SCSI...) but there's a catch.
For reasons unknown to me, DEC decided to fit these machines with their
own weird "external SCSI" connector. Meaning, you need a very special
cable (BC36 I believe) converting from their connector to the regular
Centronics-like connector. If you have or can get that, no problems.
Otherwise, either mount the CDROM drive inside the chassis, or fix your
own "external" cable using a soldering iron and some patience.

The VAX is like most systems of its class: it requires a CDROM drive
able to handle 512-byte sectors. That obviously includes the DEC
drives, but also those from Sun, SGI, IBM and a truckload of modern
drives (Toshiba, Plextor) and, for some reason, many CD-R and CD-RW
drives.

> Thanks in advance for your help! I'm really looking forward to putting
> this machine back into service...
Yeah!

Cheers,
        Fred (just done with fixing up the old DEC laptop ;-)
Received on Sun Aug 10 2003 - 13:39:01 BST