On 2020-07-10 14:19, Paul Koning wrote:
On Jul 9, 2020, at 10:40 PM, Johnny Billquist <b...@softjar.se> wrote:
On 2020-07-10 04:37, Don North wrote:
On 7/9/2020 6:25 PM, Bob Supnik wrote:
Yes, the PDP11 Architecture Handbook was a post-facto effort. The J11 was
finished; DEC did not intend to do another PDP11 processor. (I wrote a spec for
one, primarily as an exercise in trying to do a different microcode structure
than the PLA/ROM of the LSI11/F11/J11, but I lost it.) The only formal part of
the PDP11 architecture was the Commercial Instruction Set extension, DEC STD
168, which was only implemented by the F11 and the 11/44.
AND the PDP-11/74 CIS option, I might add. Fully implemented, never sold.
Not to mention that the 11/74 in itself was fully implemented, but never
sold... Not even the 11/70MP...
Were there actually two prototypes called 11/74? I know the MP machine, which
the RSX-11 development team owned. And in Merrimack (home of RSTS and some of
the compiler teams) there was an 11/74 with CIS, for COBOL. But that one
wasn't an MP machine. Perhaps a coincidence, I don't have a real memory either
way.
Well, yes and no...
The PDP-11/70MP is a modified KB11-C. In the end it's really just a
modified 11/70. There are changes to the microcode, and if I remember, a
couple of boards were changed. (See
http://www.bitsavers.org/pdf/dec/pdp11/1174/EK-70MP-TM_PRE_1170mp_Prelim_Technical_Manual_1977.pdf).
The PDP-11/74 is the KB11-E. This was a more major redesign, which then
allowed for the addition of CIS. (See
http://www.bitsavers.org/pdf/dec/pdp11/1174/Prelim_KB11-E_Diffs_Aug78.pdf).
But depending on what documentation you read, they might both be called
11/74.
Johnny
--
Johnny Billquist || "I'm on a bus
|| on a psychedelic trip
email: b...@softjar.se || Reading murder books
pdp is alive! || tryin' to stay hip" - B. Idol
_______________________________________________
Simh mailing list
Simh@trailing-edge.com
http://mailman.trailing-edge.com/mailman/listinfo/simh
