8 Apr
2004
8 Apr
'04
10:30 a.m.
In general, MicroVAX III could handle 64 Meg, though
some CPU
boards did not have all address lines brought out of Memory
Controll Unit pins. Here my memory gets fuzzy, I am not sure
whether that was the case only with those 'workstation' types
or that was also a case with backplane based machines.
The "MicroVAX III" is usually taken to mean the
MicroVAX 3600 Series (i.e. MicroVAX 3500, MicroVAX 3600,
which were the same apart from the size of the box they came
in) and the MicroVAX 3800 Series (MicroVAX 3800 and MicroVAX
3900 - again same hardware, different box). All of those could
go to 64MB by using 4 16MB memory boards - these were available
from DEC, if not from day one, certainly from very
early on.
I think there was a VAXstation 3500, which was a MicroVAX
3500 with a QDSS colour graphics board set. But that was
really just a marketing distinction - you could turn any
of the MicroVAX 3500/3600/3800/3900 into a VAXstation by
dropping in a set of dragon graphics boards.
The VAXstation 3200 was really a MicroVAX 3500 squuezed
into a BA23 case with a QDSS (if memory serves correctly).
The only reason this would not have managed to get up to
64MB would have been the lack of suitable slots in the backplane.
There
was an outfit that was retrofitting such CPU boards for full
range of addresses and I do rememmer whether they were
Stateside or in Holland.
There were outfits that produced their own memory boards,
but I think the CMCTL (CVAX memory controller chipset)
could not go beyond 64MB anyway (and probably required
four banks of memory to do that). So I doubt that any of
those 3rd party boards could have done anything "better",
other than be cheaper, of course.
Nemonix have had a history of tweaking DEC designs to
get more out of them. Whether they ever did much with
the VLSI machines (MicroVAX 3100/VAX 4000 etc) I don't
know.
The largest
Digital memory for
backplane based MicroVAX III was a 32 MB board, but that came
quite late in the life of MicroVAX III. The initial 'Minimum
Configuration' shipments of those systems were with 8 Meg,
then that was upped to 16 Meg. The 4 Meg board that is
mentioned, is probably partially populated 8 Meg layout.
However, there were third party boards up to 48 MB. Rational
for that corkey size was that customer does not have to trow
away original 16 Meg that came with machine and still fit
full 64 Meg complement into two slots.
It sounds to me like you use "MicroVAX III" to mean
MicroVAX 3100 series and VAXstation 3100 series.
In that case the early MicroVAX 3100 machines
(based on the CVAX chipset) were limited to 32MB;
they did indeed have 4MB on board.
The VAXstation 3100 Model 3x/4x machines were
also limited to 32MB of memory. The Rigel-based
VAXstation 3100 Model 76 was also limited to
32MB but used DIMMs rather than memory boards.
(The Rigel CPU could have supported more memory,
but I think they were shoving the newer CPU into
the existing VAXstation design with minimal
other changed, so they ended up being limited
to the same 32MB as the earlier machines).
The intermediate SOC-based MicroVAX 3100-30/40
machines were also limited to 32MB, the
Mariah-based MicroVAX 3100-80 could stretch
to 72MB and most (if not all) of the rest
of the NVAX-based range could squeeze in 128MB.
Antonio
--
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Antonio Carlini arcarlini(a)iee.org