PDP-11 Memory

[Pete Turnbull]

On 11/01/2019 19:59, Bill Gunshannon via cctalk wrote:

> MicroPDP box has first three slots A-B-C-D to support PMI
> memory and the rest are serpentine A-B.
> 
> Even giving a bus grant problem, I can't see that causing a CSR
> error.  I will probably have to dig out another box this weekend
> just to be sure there isn't a problem with the backplane.

Without knowing exactly what cards you've got in there, it's hard to 
tell.  There are quad-height cards that work only in straight (A.B.C.D) 
backplanes/slots, and quad cards that work in either straight or 
serpentine. There are cards that use or expect (or won't permit) certain 
signals on some pins which work fine in 18-bit backplanes but not 
22-bit.  There are things that will work in a BA11-S with H9276 
backplane (which is what you had, if it really was a PDP-11/23plus) but 
not a BA23.  You probably need to make a list of what you're using and 
check through the relevant Micronotes about compatibility.

BTW, BA23 and BA123 microPDP-11 backplanes aren't the same - it's the 
first 4 slots that differ in a BA123, and slot 13 is different again. 
Take a look at http://www.dunnington.info/public/PDP-11/QBus_chassis

-- 
Pete
Pete Turnbull