On 10/20/21 12:27 PM, Douglas Taylor via cctech wrote:
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.)
Looking at the silk screening, there is a Plessey logo so this is mostly
likely there own design. Given the date on warranty I would expect
jumpers for 18/22 bus type, perhaps battery backup, parity CSR, memory
chip size, I/O page size,etc... But assuming the jumpers for memory
address start and length are in some functional configuration, you
should to poke/read ODT somewhere in the 4MByte addressing range. You
might also try to see you can read default parity CSR for memory
boards. The logic (and some circuity) for I/O page should be different
than memory decoding.
Suggest you obtain a another memory board (e.g. M8044) to verify the
other components.
Jerry
