Subject: Re: 72pin SIMM memories
To: John A. Maier <>
From: Michael Kukat <>
List: port-vax
Date: 02/19/2000 10:31:27
Hi !

On Sat, 19 Feb 2000, John A. Maier wrote:
[PS/2-standard SIMMs and VAX memory modules]

First: I have some VXT2000s and a VAXstation 4000 VLC and tried out PC-modules.
The VXT2000 uses standard PS/2-modules, 32Bit, so they don't need parity. The
4000 VLC wants parity, the modules are standard PC 36bit. (Think it wants them
to be installed in pairs).

> The VAXstation 3100, 3520, 2540, 4000, VAX 4000 Model 100, DECsystem 5500 and maybe others use a 72pin style memory SIMM.  DEC listed them as:

If they are really 72 pins, i would say:

> MS40 parity 1-Mbit DRAM 8Meg
> MS42 parity 4-Mbit DRAM 4,8,12,16Meg
> MS44 parity 1-Mbit DRAM 4, 8Meg
> MS44 parity 4-Mbit DRAM 32Meg

These above are standard 36bit-modules

> MS44 ECC    4-Mbit DRAM 16, 64Meg
> MS60 ECC    1-Mbit DRAM 16, 32Meg

These are 40bit-modules (hard to get on the PC market)

> Though unrelated VAXstations, the DECstations, and VXT2000 also used a 72pin ECC SIMM. DEC listed them as:
> MS01  parity 1-Mbit DRAM 4Meg
> MS01  parity 4-Mbit DRAM 4Meg
> MS01  parity 4-Mbit DRAM 16Meg
> MS02  ECC    4-Mbit DRAM 8,32Meg
> MS200 unknown       DRAM 2,4Meg
> MS220 ECC    4-Mbit DRAM 64Meg
> MS220 ECC    1-Mbit DRAM 32Meg

Here i can say more sure, that PC modules should work

> Will a VAXstation work with memory void of ECC?  

I don't think so. If it really wants ECC, it will need it.

> Are they EDO style memory or Non-EDO?

They are all old FastPage RAMs. Te get sure, you should just plug in some PC
modules and check them, if they work. There are no crazy things like +12V at
some address pins or so, i didn't ever destroy a module in my machines.

> I'm sure I'm not the first to be tempted by such similarities.  

Sometimes, questions of this kind go through the list. Ah yes, to get this
cleared up finally: I just tried 16MB-modules in the VAXstation 4000 VLC. It
definitely DOESN'T work, so 24MB seems to be the maximum for this machine.


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