Where to get a Vax or microvax

Johnny Billquist bqt at update.uu.se
Mon Jun 29 13:52:17 CDT 2015

On 2015-06-29 18:08, tony duell wrote:
>> on real hardware. What would be the best machine for a beginner to VAX
>> Hardware to start out with?
> I think you need to think very carefully about what you want this machine to do.
> The ideal VAX for me is not going to necessarily be the ideal VAX for you.
> In general there are 3 classes of VAX that people run at home. There are many
> other families, but in general they are much rarer, and probably much harder to
> maintain.
> The first series are the VAXstations, probably a 3100 of some kind. These are
> desktop boxes, they are workstations (so you can drive a CRT monitor from them,
> although they have serial ports too, and AFAIK can use a serial console). They
> generally have SCSI and ethernet interfaces built in. The downside is that they
> are somewhat closed machines. You have connectors for a memory board in
> most of them. You have the SCSI bus for disks. But you don't really have access to
> the CPU bus to add anything out of the ordinary. This may well not matter to you.
> The second series are the MicroVAX II/III machines. Normally in a deskside-size
> cabinet. Normally use a serial terminal, but there are exceptions. Here the CPU is
> one board, memory is one or 2 more, then separate boards plugging into something
> called Qbus for everything else. The advantage, of course, is that Qbus is the processor
> bus so if you need a strange interface you can probably add it. The disadvantage is that
> finding some of the boards you may want is a pain (Qbus SCSI is often hard to get)
> The third series I hesitate to mention, as I don't think they're what you are looking for. That's
> the first ever VAX series, the 11/7xx machines. There are 3 sub-families. The 11/780 was the first
> It's massive (think large wardrobe just for the CPU) and needs 3 phase mains officially. The
> upside for a hardware person is that said CPU is massive because it's built from lots of simple,
> standard, ICs. It's repairable. Very. The 11/750 came next, a bit smaller, but now the CPU is
> a lot of custom gate array chips. One that I would avoid (yes, I know I'll get flamed for that from
> all the happy owners). To me the 11/750 is large and doesn't give you anything over a microVAX
> The third subseries is the 11/730. It's slow. It's very slow. I am told that using the DEC supplied
> microcode tape it can take 25 minutes to get a boot prompt (!). But it's small, the CPU is one
> 10.5" high, 19" wide rack mount box. A useable machine fits in a half-height rack. And amazingly
> this small VAX was built from standard ICs (admittedly a lot of PALs), mostlly. These machines use
> an expansion bus called Unibus (the 11/780 and 11/750 also have MassBus for disks). Unibus is
> similar in concept to Qbus, so again you would have a board for ethernet, one for serial terminals,
> etc.
> For me, a hardware hacker with too many machines as it is, the 11/730 fits the bill. I can accomodate
> it (I doubt I could fit an 11/780 in anywhere) and I can hang a logic analyser off it if I want to. For you,
> I think you should probably look towards a VAXstation to start with. But I might be very wrong...

So, where would you place a VAX8650 in there? Or the 6000- or 
7000-series? :-D
(Or, drool, a 9000?)


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