Looking for info on memory

[Douglas Taylor]

On 10/19/2021 12:57 PM, Nigel Johnson Ham via cctech wrote:
> I am trying to bring up an 11/23 system in a BA23 box, and the only
> memory i have is an obscure Plessey one. The only identification is the
> p/n 705920 with dash-100 in white ink. By counting the chips I make it
> 4MB, but it does not respond. Since it takes the full 22-bit memory
> space I can't see how any jumpers would change its accessibility. Does
> anybody have a manual?
>
> any help appreciated,
>
> Nigel Johnson
>
Looking at the photo I began to wonder if Plessey made their own boards 
or are they re-badged from some other manufacturer.   I don't know.  If 
they are made by someone else, you might be able to dig up a manual.

Also, if you look at the documentation for other 4MB qbus memories how 
many jumpers do they have?  And what do they do?  It may help you 
understand your board.

Doug  (of course I don't have a 4MB qbus memory, but that apparently 
didn't stop me from posting.)