11/21 Falcon board, ie KXT11-{AA|AB|BA|CA} is a single-board,
"Dual-wide" (to use DEC descriptions counting the number of contact
finger groups on the card-edge) for earlier versions, quad-wide for -CA
PDP-11 CPU board with integrated memory and 2 or 3 serial ports. The
last version could have memory up to 64 kB on-board, slightly earlier
version max 48 kB, the first version 4 kB. "The OEM computer" of those
days - compare it to an ARM or PIC-chip of today. CPU is the T-11 chicp,
ie generation 2 out of 4 integrated generations. Picture of dual-wide
type at: http://www.conticomp.com/item_show.cfm?itemID=157659
BUT: The last fine PDP-11 by DEC was the PDP11-93 CPU. This was built as
a single-card computer, quad-wide Q-bus, integrated memory (2 or 4
MBytes depending on version/price), integrated 8 serial lines,
integrated boot-rom etc. CPU is the J-11, ie generation 4 out of 4
integrated designs.
So, physically, both these are the same, but the later has more of
horsepowers in it's CPU. Both of them would do the job you have
described, the latter would do it eassily...
(All "early" PDP-11:s were built upon MSI logic, so a CPU would need at
least a few cards, each hex-wide size.)
When it comes to the architecture, The PDP11-20 (with oem name PDP11-15)
was first. This one ha the "smallest" architecture, with a minimum of
features. To design the "smallest" PDP-11 emulator, an 11-20 should be
emulated (I think there is an FPGA-code on the net for this CPU). This
one has 16 bits of adress, ie max 64 kB memory.
For OS:es, RT-11 is certainly the "smallest" of those that were offered
by DEC in the later part of the PDP-11 era. RT-11 can run on most system
configurations, using minimum floppy or TU-58 tape drive as secondary
storage.
The TU-58 tape-drive was connected using one serial port. PC-based
emulators of this 1/4" tape drive exists freely today (using PC with
COM-port).
One small system to "copy" in config could possibly be a PDT11-150 or a
VT103 aka PDT11-110 and/or PDT11-130. Actual config of these should be
possible to find online...
As for emulations, this coule of today be run in a system not much
larger than a coin...
More information can be read at:
http://hampage.hu/pdp-11/main.html
http://en.wikipedia.org/wiki/PDP-11
and at lots of other fine sites through the net.
/Göran
On 2012-07-05 19:03, Alan Frisbie wrote:
And people who "know" PDP-11s are asking them self "smallest
pdp-11", what is that?
The smallest one I recall was put together by John Crowell,
and was based on an 11/21 "Falcon" board. My memory is a
bit hazy (hey, it was 30 years ago!), but it had one or two
TU58 drives and ran RT-11 (anyone who knows John would not
be surprised by that). Since it was used for collecting
data in the field, he called it the Field-11.
Somewhere in my archives I have a magazine article about it.
I'm sure there were even smaller ones based on the T-11 chip.
Alan Frisbie
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