On 07/09/2016 13:02, Noel Chiappa wrote:
From: Pete Turnbull
all microPDP-11/73 machines had an M8190. The M8192 was mostly sold
as an OEM board.
That's so bizarre (although the "Supermicrosystems Handbook", which
covers the 11/73, confirms it used the KDJ11-B).
As does the MicroPDP-11 Systems Maintenance Manual, the Micro-PDP-11
Handbook, some Micronotes, the MICRO/PDP-11 Technical Manual, the IPB, ...
So the KDJ11-A
(M8192) was not used in any 'PDP-11/xx'?
Unless DEC sold something like a PDP-11/73S in a BA11-S chassis (like a
PDP-11/23plus), it was only used for OEM systems and customer-fitted
upgrades.
The other thing that makes no sense is that the KDJ11-B (M8190) has
all that extra circuitry on it to support PMI, etc - all of which is
unused in the 11/73 application! Why not just plug in a (presumably
cheaper) M8192? In the /73 application, the two are basically
equivalent. (OK, there are two built in serial lines on the M8190 -
big whoop.) Both have 8KB caches (although the one in the M8190 has
slightly fancier tagging, IIRC), etc, etc. Maybe it's the ROM (which
the M8190 has, but not the M8192)?
Don't forget the LTC :-) All in all it saves a decent amount of
backplane space, makes field service easier, and follows DEC's attempts
to integrate as much as possible. Otherwise, you'd need an additional
bootstrap card such as an MRV11-D with -B2 boot ROMs, a DLVE1 (DLV11-JE)
for the SLUs, something with an LTC, and termination. That's at least
twice as many slots in a Q-Q backplane and four slots in Q-CD. A BDV11
wouldn't work as it doesn't have the ROM capability (well, one of mine
does but it's been seriously modified, well beyond the ECO for 22-bit
:-)). OK, you could use an MXV11-B with -B2 boot ROMs, but that's an
expensive way unless you just want a very small (and slower) system, and
you might still need termination.
And don't forget that DEC sold the microPDP-11/73 as a lower-cost
alternative to the microPDP-11/83 which didn't appear until slightly
later, or looking at it another way, as a fancier and faster
microPDP-11/23. The very first boards had some ASIC/J-11 problems that
meant they wouldn't work with an FPJ11, and the first J-11 CPUs wouldn't
run nearly as fast as intended so they were fitted with 15MHz crystals
(as-sold-by-DEC 11/83 systems have 18MHz crystals). I couldn't possibly
imply they were finding a way to sell the inferior parts. After that
it's probably all marketing differentiation.
--
Pete
Pete Turnbull
