On 10/21/2020 11:36 AM, Noel Chiappa via cctalk wrote: > > From: Jay Jaeger > > >> 2--M7134 KT24 Memory map > > > M7891 UNIBUS Memory (256K, I think, presumably addressed for 0). > > If that's all the memory you have, the KT24 isn't really doing anything > (well, monitoring power; holding boot PROM's; etc). Is your MS11-L configured > to be EUB memory, then? If no KT24 is plugged in, the CPU detects that there > isn't one there, and permanently, statically maps the UNIBUS straight across > to the bottom 256KB of EUB space. (Presumably a low-cost option for the /24.) >
No idea how it is configured as it has always "just worked". Factory as a guess. Will pull it and document it. > Although the 'straight across' mapping only applies to UNIBUS->EUB cycles, > not EUB->UNIBUS cycles, such as those from the CPU; but the TM says [pg 2-31 > in the 003 version] that if E124-S6 is OFF, "the lower 18 bits of every > address go to the UNIBUS", which implies that when OFF, UNIBUS memory appears > at 0 in the CPU's address space. So it should work as UNIBUS memory, with > E124-S6 OFF; it would be interesting to verify that. The TM also says (pg. > 2-40) "systems with UNIBUS memory ... require changes to be made to the > mapping jumpers [on the KT24]". > > > Let me know if you want me to go thru the process of > > .. > > 2) Pull the boards and document > > What kind of box is your -11/24 in, a BA11-A, or BA11-L? > > If the latter, I'd be really grateful for some closeups of the interior, so I > can put mine back together, and do some of these experiments. (Yes, yes, I > know I should have taken pictures before I took it apart; I was just > starting, and was going by how we used to do things, back before there were > digital cameras.) I could probably work it out by staring hard, and thinking > harder, along with the prints, but photos would be a lot easier! :-) > > If it's a BA11-A, I'm still trying to get an image of the special power > adapter used to turn the bus bar of the BA11-A into the 6/15 pin Mate-N-Lok > connectors used by the -11/24 backplane. > > Noel > It's the BA11-A - 10.5" flavor. I'll take photos you requested here and document the board jumpers and switches over the next week or so, for my own use, if nothing else. JRJ
