[rescue] Finding antique machines

Carl R. Friend crfriend at rcn.com
Fri Apr 20 17:56:51 CDT 2007

    On Fri, 20 Apr 2007, John Francini wrote:

> Meanwhile, the original Monitor was dubbed "TOPS-10", and the system
> as a whole was christened "DECsystem-10" when the second processor in
> the family, the KI-10, came out in 1972.  It was twice as fast as the
> KA-10, used 512-word pages instead of the 1Kword-multiple memory
> segments of the KA, would allow individual pages to be set
> write-protected or write-enabled, and could support non-contiguous
> job memory spaces.  However, TOPS-10 still didn't support it.

    The -10 Monitor supported the KI-10 just fine.  I've worked on
it.  Later versions even supported (barely) the notion of non-
resident pages on the KI, although it was positively painful to
work with in that mode.

> The KL-10 Model A, which came out in 1974, was Digital's first
> microcoded processor. It was twice as fast as the KI-10 it replaced.
> It supported KI-10 style paging, which was just fine for TOPS-10.  It
> also supported external memory channels, which allowed it to be a
> 'drop-in' replacement for the KI-10.

    DEC's first "production" microcoded machine was the PDP-9, if
I recall correctly, and it used a variant of "core rope" for its
micro-store.  DEC later learned the error of their ways in that
regard with the PDP-15, but this obviously didn't penetrate the
rarefied -10 atmosphere.

    The KL was a smoke-and-mirrors machine, and the bulk of that
trickery was it's cache memory.  Whilst that cache was laughably
small by today's standards, it did make the KL seem to be a
screamer.  The interesting truth is that with the cache turned
off the KL was actually slower than a KA.  This, in a sad way,
puts the KL into the early category of "shove the bottleneck
around" systems where balance no longer matters -- and we suffer
maddeningly for that architectural mistake today.

> A single-box, cost-reduced (and 4x slower) model, the DECSYSTEM-2020
> (also known as the KS-10), was released in 1978.  It used a PDP-11
> UNIBUS for its peripherals, and also supported both TOPS-10 and
> TOPS-20.

    The KS remains a very nice single-user (or small number of
users) machine.  It's performance is about that of a PDP-6, its
data-channels are pathetically slow, and its I/O is roughly
that of an -11, but at least it runs the -10 instruction set.
They make fine home machines if you feel the need to run "physical
iron".  They were moderately successful in the real world for
small shops with limited applications.  KLs are too expensive to
run nowadays, and I do not believe that there are any more KIs
(the ultimate -10) in runnable condition anywhere.

| Carl Richard Friend (UNIX Sysadmin)            | West Boylston       |
| Minicomputer Collector / Enthusiast            | Massachusetts, USA  |
| mailto:crfriend at rcn.com                        +---------------------+
| http://users.rcn.com/crfriend/museum           | ICBM: 42:22N 71:47W |

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