11 Jan
2019
11 Jan
'19
12:38 p.m.
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