applicationDEC 433MP

From: Mark Gregory <>
Date: Tue Jan 23 00:26:14 2001

I spent an enjoyable weekend dissassembling, cleaning, and re-assembling a
433MP (introduced 1990, so just on-topic). It came from an industrial
environment, and was one of the filthiest computers I've ever seen. I didn't
get any manuals, and there's very little info about these machines on the
Web (Compaq, as usual, pretends these machines never existed), so I was
hoping one of list DECkers could help with a few questions:

- the machine has 2 memory boards, which give a maximum of 32 megs of ECC
RAM, with 40 x 1 meg SIMMs. Can the system use more than 2 memory boards, to
go to 64 megs? Or can the 1 meg SIMMs be replaced by 4 meg SIMMs?

- on powerup, the system BIOS reports 640K of main memory, and 13312K of
extended memory; there are 25 x 1 meg SIMMs installed, so I'm expecting 20
megs after subtracting the ECC SIMMS. Any ideas why the BIOS isn't seeing
all of the available RAM?

- the system has 2 x 486/33 processor cards installed - one base CPU card,
and one CPU/SCSI card. The system can hold up to 4 processor cards; were
there any OSes that could use 4 processors at a time? Is it worth hunting
down two extra CPU cards?

- there's a TZK10-AA tape drive in the system. What tape cartridges does
this drive use?

- the processor cards use Intel 80486 DX chips at 33 Mhz. I dimly recall
that the 80486DX2/66 is a drop in replacement for the 80486DX33. Can I get a
quick speed boost by swapping the processor chips?

- finally, how popular were these machines? They're nicely built and
engineered, but I had never heard of them before I found this one, and the
MicroPDP-11 that I got with it ... but that's another story.

Thanks a lot for any help.

Mark Gregory
Received on Tue Jan 23 2001 - 00:26:14 GMT

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