uVAX II Memory Board

From: Jerome Fine <jhfine_at_idirect.com>
Date: Fri Feb 2 21:09:51 2001

>ajp166 wrote:

> >I have an interesting question. Can this board be used as additional ram
> >in a PDP-11? If so, how might it be done?
> >I have a Qbus Memory board that must be from a uVAX II - M7609-AP
> >with 288 (I hope I counted correctly) memory chips
> >4256L-15 8726255 A 21-22422-42 R with the
> >a standard male 50 pin header at the top to be connected to a uVAX CPU.
> >If my arithmetic is normal, does this make it an 8 MByte memory?
> It's a microvax memory most likely. PDP-11 can address a maximum of
> 4mb.

Jerome Fine replies:

Yes and YES!

> >But, is there any way that a regular PDP-11/73 could see this memory
> >and use it in some manner?
> No, it's not compatable.


I heard some time back that either you or Megan Gentry had converted
an old DEC Qbus memory board to be a RAM: disk of some sort.
Maybe I was mistaken in that it was just normal memory - above the
usual PDP-11 memory and with an address gap - and the PDP-11
did all the extra software to make the memory look like a disk.

> >I don't expect that anyone will want it, but if so, can I swap it for a regular
> >PDP-11 Qbus memory of 4 MBytes?
> That should be possible but I think the largest common memory board
> for PDP-11 Q-bus is 1MB.

DEC made a MSV11-CA and there were a number of third party 4 MByte
memory boards. I remember that Chrislin made a single 4 MByte quad
memory board.

As for PMI memory, DEC made the MSV11-JD at 1 MByte and the
MSV11-JE at 2 Mbyte for the 11/83. I don't seem to remember that
DEC made a 4 MByte PMI memory. If SIMMs had been around 10
years sooner, DEC could have put those right on the CPU board. Of
course if the Pentium had been around 10 years sooner, maybe DEC
would have made a better PDP-11.

Sincerely yours,

Jerome Fine
Received on Fri Feb 02 2001 - 21:09:51 GMT

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