Qbus split I&D?

Noel Chiappa jnc at mercury.lcs.mit.edu
Tue Mar 17 18:30:21 CDT 2015

    > From: John Wilson

    > I think Guy's MEM11 is going to be way cooler. ... I'll be doing a new
    > rev one of these months ... and then I'll certainly make them
    > available, but not seriously expecting anyone to order one. Guy's MEM11
    > is nicer!

Yeah, but for some machines I wouldn't mind having pure memory boards.

    > it plugs into the A/B positions of a MUD/SPC slot, which makes it
    > useless on an 11/20 which doesn't have those (right? unless you add a
    > BA11K?)

I haven't checked, but I suspect there might be a way to power like a DD11-C
through some sort of conversion plug, but I'm not up on 11/20 power (would
have to read the H720 manual, which I'm too lazy to do).

    > Naturally I've gotten way sidetracked writing that firmware ...
    > Totally out of hand.

Hah, what else is life for? :-)

    > it sounds (from the MS11P manual) as if the 11/24 and 11/44 extended
    > Unibus would be easy to support as an option (seems like the four extra
    > address bits on AN1, AP1, BE1, and BE2 are all that's new

I'm pretty sure. If you look at the MS11-M prints (FMPS #742, pg. 4), they
have a jumper called 'UNIBUS/Extended UNIBUS' and basically all it does is
disable listening to those 4 extra bus address lines. (It also affects CSR
stuff, but not the basic memory operation, other than disabling the 4 extra
address lines.)

I've got some MS11-P cards (which are now really cheap, compared to real
UNIBUS MOS memory) here, and I'm planning on hacking them so they are UNIBUS
cards, via a similar hack. (I'm not going to use MS11-M cards because they
use some wierd voltage that's only easily available in the 11/44; the
MS11-P's use +5V only.)


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