[TUHS] Unix on PDP8?

Clem Cole clemc at ccc.com
Thu Nov 30 00:05:22 AEST 2017

On Wed, Nov 29, 2017 at 1:56 AM, Lars Brinkhoff <lars at nocrew.org> wrote:

> The tiny instruction set is surprisingly versatile!
​The precursor to today's VHDL and Verilog was a language called ISPL /
ISPS.    There were many ISPS ​descriptions of different systems being
written in those days.  I bring it up because, the PDP-8 - aka 'mini', ISP
was a single 66-line lineprinter page long.  Which was astounding, when you
compared it to the ISP descriptions of the PDP-9/10, the IBM 360 *etc*...
Even the PDP-11 ISP is a many pages because of all the addressing modes.

Remember, Gordon Bell's term 'mini-computer' was not describing a 'small'
computer, but instead it was a 'minimal computer.'   It was only when the
microprocessors were created a few years later that the term was warped to
mean  'small' by the computer press.

As a side note of UNIX history (thank you Will for the reminder) ...
 another piece of my to do list is get ISPS running again.   The original
version was in BLISS-10, then compatible BLISS (Vax) on VMS which Danny
Klein and I worked on.  The BLISS version generated net-lists for DEC
PDP-16 RTM modules, [which I'm sad to say are a lost art and I fear may
have been lost to history.  I may be one of the last groups that ever
designed with them.  It was DEC productization of the 'flip chips'
originally created for the PDP-7 and PDP-8.  IIRC you can read about them
in the DEC 'blue book'].

But the late Ted Kowalski's PhD thesis was a C implementation that ran on
the CMU's V6++ UNIX / PDP-11 [that actually generated moclisp as the parse
trees - very interesting system].   Ted wanted to go to transistors
directly in the back-end.  Working with this thesis advisor at the time,
(Don Thomas) an improved version of Ted's work, would become VDHL - which
Don wrote all the books, in the 1990s.

Besides traditional word processing (troff et al) and C program
development, ISPS was one of the first 'production' use of UNIX I saw.
Trying to generate 'chips' automatically from HW descriptions in the late

Anyway, if you find a copy of the Sieworwick, Bell, and Newell's book
'Computer Structures, Reading and Examples', there is a companion volume
that has many of the ISPS descriptions of the machines discussed in the
main text.   As Will's note about HP points out, as historians we should
try to find them all and get them in bitsavers or the like.  I know I have
some of the ISPs for the micro's and the PDP-11 on hardcopy in a filing
cabinet (I just ran into them a few weeks ago when looking for something
else), but I should have them on tape.   It would be a shame to lose those.
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