7 Feb
2006
7 Feb
'06
1:15 p.m.
Don North <ak6dn at mindspring.com> wrote:
Found when I was going thru a box of DEC memorabilia
... an original
11/74 front panel (plexiglass only). You can tell it is from a 'true'
11/74 as it has front panel positions for the commercial instruction set
microengine (CIS uADRS, CIS DECIMAL datapath, and CIS DESCRIPTOR datapath).
Here's a pix: http://www.ak6dn.com/stuff/1174.jpg (not the best
quality, done on a scanner, not by camera). I need to figure out a way
to get the LED positions to light up. Maybe I'll build a LED board and
hook it up to my 11/34...
Very nice!
However, a few things I've wondered about for a long time.
This is obviously a panel for a corporate cabinet. I've also seen a
picture of an alleged 11/74 that was in a corporate cabinet.
However, the one picture I've seen in real life (as opposed to on the
internet) of an 11/74, it was in full height 19" cabinets with the
traditional maroon/red color scheme.
Also, I am under the impression that a CIS was never completed. That
would have required the KB11-E. The only 11/74 CPU I know was done was
the KB11-Cm, which is a modified KB11-C (aka 11/70). This won't allow
you to add a CIS option. No place nor wiring for it.
Does anyone know *for sure* that the KB11-E was made, or might this
front have been a prototype for a possible KB11-E, but in reality used
just with a KB11-Cm?
(Oh, and for those of you who care... login to mim.update.uu.se as
guest/guest, and run RMD...)
Johnny
--
Johnny Billquist || "I'm on a bus
|| on a psychedelic trip
email: bqt at update.uu.se || Reading murder books
pdp is alive! || tryin' to stay hip" - B. Idol
7 Feb
7 Feb
2:05 p.m.
Johnny Billquist wrote:
Don North <ak6dn at mindspring.com> wrote:
The 11/74 was basically an 11/70 as the core
CPU (a couple of CPU boards
were actually updated to provide hooks for the CISP) and a revised
backplane to handle the multi-card CIS 11/74 option. The 11/74 used the
same physical chassis as the 11/70, so it could easily be mounted
anywhere a classic 11/70 could be.
Found when I was going thru a box of DEC
memorabilia ... an original
11/74 front panel (plexiglass only). You can tell it is from a 'true'
11/74 as it has front panel positions for the commercial instruction
set microengine (CIS uADRS, CIS DECIMAL datapath, and CIS DESCRIPTOR
datapath).
Here's a pix: http://www.ak6dn.com/stuff/1174.jpg (not the best
quality, done on a scanner, not by camera). I need to figure out a
way to get the LED positions to light up. Maybe I'll build a LED
board and hook it up to my 11/34...
Very nice!
However, a few things I've wondered about for a long time.
This is obviously a panel for a corporate cabinet. I've also seen a
picture of an alleged 11/74 that was in a corporate cabinet.
However, the one picture I've seen in real life (as opposed to on the
internet) of an 11/74, it was in full height 19" cabinets with the
traditional maroon/red color scheme.
Also, I am under the impression that a CIS was never completed. That
would have required the KB11-E. The only 11/74 CPU I know was done was
the KB11-Cm, which is a modified KB11-C (aka 11/70). This won't allow
you to add a CIS option. No place nor wiring for it.
The multiprocessor version of
the 11/70 was not *really* the 11/74. The
11/70MP modified the microcode for the ASRB instruction to define it as
the atomic lock primitive (forcing a DATIP/DATOB cycle instead of a
plain old DATI/DATOB). It also added the IIST (interprocessor interrupt
and sanity timer) for interprocessor interrupt capability and a watchdog
timer.
The 11/74 and CISP were most certainly completed. I know first hand
because I worked on them and was one of the three microcoders that wrote
about 4K of 96b microcode to implement the PDP-11 commercial instruction
set. The complete irony is the same day that engineering signed off the
system to manufacturing, releasing all the hardware and PROM code to
production, DEC product management killed it. They finally decided that
high-end PDP-11s should be EOLed in favor of the newly released
VAX-11/780 (this was in 1979 IIRC). The 11/44 CIS project started up
shortly after the 11/74 CIS, but it had a much lower performance target.
It actually did ship to customers.
Part of the problem was that we did too good a job (IMHO anyway :-).
PDP-11 Cobol performance (the Cobol compiler actually used CIS
instructions) on an 11/74 was a factor two or better than that of the
11/780 running the same Cobol program. Marketing could not figure out
how to push the new 11/780 into commercial accounts when the 11/74 was a
clear performance winner. Of course the real benefit of the VAX was the
32b architecture, allowing programs larger than 128KB (I/D) without
having to resort to overlays (disk and/or memory swapping).
Does anyone know *for sure* that the KB11-E was made, or might this
front have been a prototype for a possible KB11-E, but in reality used
just with a KB11-Cm?
Yes, the 11/74 KB11-E was finished by engineering (started in
the Mill,
moved to Tewksbury) but abandoned by DEC marketing. Some number of proto
systems were around for a while being used internally within DEC but I
don't believe the 11/74 was ever offered externally.
Don North
DEC 1975-1982
(Oh, and for those of you who care... login to mim.update.uu.se as
guest/guest, and run RMD...)
Johnny
6745
days inactive
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