Tony Duell wrote:
Silly random thought. IIRC, there's an empty 40 pin
DIL socket on the ACW
coprocessor board, and I think it's on the 32016 sencond processor board
too (I must come and collect that from you). Wasn't that for an MMU chip?
Yep, you're right (about there being empty sockets on both versions of
the board). I suppose it's logical it'd be an MMU chip given that
there's no other connectors to the board (e.g. it's not for an optional
serial chip or whatever).
I've checked my ACW schematics, and it is for an 32082 MMU chip.
Funnily enough, mention of that socket just cropped up on the BBC list,
and someone remembers their father working on one of these boards with a
floating point unit fitted into that socket via a small daughtercard.
They're willing to admit that they may be misremembering though!
Would that be a possibility though, or is it definitely an MMU socket?
They're going to mention it to their dad, but suspect that he's long
since forgotten details too.
(Incidentally this was at Oxford uni - which is the first time I've
heard that they had any 32016 units, although I suppose it's not surprising)
Oh, and I was also thinking about the Xenix on the ACW rumour. It's
remotely possible that someone managed to get Xenix running on the 80286
coprocessor in the ABC 3xx machines I suppose, and that's where this
rumour of ACW's running Xenix started (after all, the machines look
identical externally). It'd solve the porting to a different CPU issue
at least, but presumably would be no small feat to get it to do I/O
across the TUBE. Still, slightly more plausible than an ACW version...
I could see Acorn doing early press releases about the ABC range and
saying "oh yeah, we've got Xenix in the works for one of these" - and of
course to most people the ACW and the ABC equate to the same system as
the Z80 version's largely forgotten and the 80286 version never existed
outside the labs (far as I've been able to tell). Hence over time things
got corrupted into people thinking there was a 32016 Unix variant...
cheers
Jules