CDC 6600/Cyber 73 Memories - WAS: Harris H800 Computer

Chuck Guzis cclist at
Thu Apr 21 18:33:55 CDT 2016

On 04/21/2016 01:36 PM, Paul Koning wrote:
>> On Apr 21, 2016, at 3:55 PM, Chuck Guzis <cclist at> wrote:
>> ... Ten was a number that figured into various aspects.  The clock
>> was nomially 10 MHz;
> In serial numbers 1-7 only nominally -- the clock was a ring
> oscillator, tuned by tweaking wire lengths.  Starting with serial
> number 8, there's a crystal oscillator (in the ECS controller if ECS
> is present, otherwise in the CPU).

Yup, that's why I used the word "nominally".  The clock distribution
circuitry in the 6600 was a study all by itself.   Mike Miller said that
his first job right out of school was measuring the various loops on the
back of the machine at Chippewa Falls to which Seymour had attached tags
that simply said "tune".

> I thought the 70 series (6000 series) was 131 kW max because the top
> bit is the "ECS active" bit.  170 series makes it 262k.

IIRC, the SCOPE aka. NOS/BE team at SVLOPS didn't have access to a real
operational 170, so a 70 was jerry-rigged by the CEs there for
development purposes.   There was a lot of weird stuff at one time in
Sunnyvale.  We had the only extant STAR 1-Bs for a time, for
example--mostly held together with chewing gum and baling wire, it
seemed.  Took hours to compile a kernel--if the machines stayed up that

> Neat.  PLATO made extensive use of ECS, swapping per-terminal state
> and programs in and out of ECS for fast interactive service.  ECS was
> also where most I/O buffers went, with PPUs doing disk and terminal
> I/O from/to ECS rather than central memory.  A dual mainframe 6500
> system (4 "unified" processors total) did a decent job supporting 600
> concurrent logged-in terminals, out of a total of 1008 connected.
> That was around 1977 when I worked on that system at the U of
> Illinois.

Was that UIUC?  I processed some CYBER tapes from there a couple of
years ago--there's an archivist there who uses us to retrieve contents
of various dusty items.


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