Help: PDP-11 instruction classification (again!)

Tim Shoppa SHOPPA at
Thu May 11 03:06:12 AEST 2000

>Some models are listed as (see XXX), where XXX is a CPU model used in
>that machine.  Are there more opportunities for doing that?  It would
>be nice to have two tables: "Machine model 11/NN used CPU models X11 or
>Y11."  "CPU model X11 had features A, B , and C."  Or something like

It's complicated by the fact that often the same CPU module was used in
differently DEC-labeled systems.  For example, a late-rev KDJ11B with
PMI memory in a Q-bus is an 11/83; the exact same CPU board with non-PMI
memory in a Q-bus is an 11/73.  And the exact same CPU board in a very
different backplane is an 11/84.

And an 11/73 can also have a KDJ11A in it, a very different module.
See Micronote #39.

At one point I began writing up a "KDJ11-x" FAQ, but never got it
finished.  There are many variations between different revs of the
J11 CPU chip and the boards, especially with respect to whether
FPJ11's work properly or not.  Many (but not all) of the KDJ11 differences
are well described in Micronote #39, _KDJ11-A and KDJ11-B Differences_.

(Side hint: everyone should have a copy of the Micronotes.  If you don't
have a printed set, you can read them online at

by clicking on "Micronotes").

>53     (see J11) (KDJ-11D?)

Yes, the 11/53 is a KDJ11-D.

>93     (see J11) (KDJ-11D?)
>94     (see J11) (KDJ-11D?)

93's and 94's are KDJ11-E's.

>J11 = KDJ-11A or KDJ-11B

And lots of other systems.  Some DEC peripherals (most noticably the
early HSC storage controllers for VAXclusters) have J11's, several Xerox
laserprinters used J11's, DEC PRO380's used J11's.  Many third-party
CPU boards use J11's, it's not unusual to see them scrounging the used
market for HSC's to strip the J11 from, as the HSC's generally had late-rev
J11's.  (And Harris hasn't made the J11 chips for many years now.)

>T11 = ?

Never sold as a "PDP-11" system, though the chip does implement the
basic PDP-11 instruction set (and some of the add-ons.)  It was sold
by DEC in the KXT11-CA single board computer, which had a T11, 32K RAM,
up to 32K of EPROM, 3 serial lines, some parallel I/O, and a Q-bus
interface.  For more information see

  Micronote #16, _KXT11-CA Development Tools_

  Micronote #18, _KXT11-CA DMA Programming_

  Micronote #32, _KXT11-CA Parallel I/O_

  Micronote #34, _Programming KXT-11C Multi SLU_

You can find T11 chips in several Q-bus and Unibus peripherals, most notably
the RQDX1, 2, and 3 (the chip labeled "27-17311-01").

>F11 = ?

aka "Fonz-11", the CPU chipset used in 11/23's, 11/24's, the lower-end
DEC PRO's, etc.

The CPU chipset used in the LSI-11/02 and /03 is a Western Digital chipset,
and the same set was used (with different microcode) by other CPU makers.
In particular, the Alpha Micro two-board S-100 set.

 Tim Shoppa                        Email: shoppa at
 Trailing Edge Technology          WWW:
 7328 Bradley Blvd		   Voice: 301-767-5917
 Bethesda, MD, USA 20817           Fax:   301-767-5927

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