Differences between PDP-11/83-84 M8190-AB/AC and AD/AE CPU cards

Holm Tiffe holm at freibergnet.de
Thu Feb 5 14:12:15 CST 2015

Noel Chiappa wrote:

> So I've seen some references which say that the M8190-AB and -AC (w-o/w FPJ11
> FPP chip) are 15 MHz "11/73" CPUs for QBUS use, and the M8190-AD and -AE
> (w-o/w FPJ11) are 18 MHz "11/83-84" CPUs for UNIBUS use (via the KTJ11-B
> convertor, of course). (Of course, the /83 is nominally QBUS, but let's ignore
> that for the moment... :-)
> (And I'm not even going to try to give the KDJ11- suffixes that go with
> these... :-)
> However, I'm wondering if this is correct... I have a CPU board out of a 11/84
> (one owned by DEC, no less!) which says M8190-AB on the handles, but the clock
> crystal says "18.432", and it has a 57-19400-09 J11 chip, which seems to be
> the 18MHz version (the 15Mhz seems to be -04).
> Comparing it to a 'stock' -AB, this one seems to have the same 74S472 PROMs
> (6 along the lower left-hand edge), PALs (top center and lower left), etc.
> But they also match the ones on a 'stock' -AE, too!
> So clearly an -AB/AC _can_ be _upgraded_ to an -AD/-AE... but are there
> actually any differences between an -AB/AC and an -AD/-AE, other than the
> speed?
> I don't have my /84 up yet, so I can't plug a stock -AB in and see if it
> works, but I'm starting to get the impression that except for the speed of the
> J11 (and the crystal), and whether or not it came with the FPJ11, all four of
> these boards are otherwise identical. Whether it's a 73, 83 or 84 depends
> entirely on whether it has PMI memory and the KTJ11-B UNIBUS converter (and
> the correct backplane, for the latter, of course).
> Anyone have an confirmation one way or the other? Thanks!
> 	Noel

I've upgraded my Board from 15 to 18Mhz, changed the xtal and the J11,
works flawlessly on 2.11 BSD with PMI memory and FPU.


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