On Jun 21, 2021, at 3:52 PM, Chuck Guzis <cclist at
sydex.com> wrote:
On 6/21/21 11:53 AM, Paul Koning wrote:
Perhaps you were thinking about the CDC 6500 at
the late lamented LCM? That got some replacement stacks, which was an interesting puzzle
because the read data connection out of the memory modules is a differential analog signal
carrying the sense wire data, so the replacement module had to produce signals of that
form.
No, it was definitely a CHM project--could have been for the 1401,
though. In way of comparison to the 6000 core, 1401 and 1620 memory
is much larger, less dense and slower--and I don't believe that the
machine architecture makes use of a read-modify-write that the 6000 so
neatly exploited.
From whence did the LCM 6500 come?
--Chuck
Some vague memory says Purdue. LCM actually got it running, which was an interesting
problem. It required recreating the inter-chassis cables (since the original ones were
cut as part of dismantling the machine) and restoring the cooling system. That was a bit
tricky since it uses non-PC coolant, which actually still exists but can't be
manufactured any longer -- you have to use whatever recycled material still exists in the
world, and find a graybeard AC tech who knows how to work with the stuff.
I think the machine is pretty much original except that a few core stacks were busted so
they were replaced by RAM based emulations. And it may be that the original console
display wasn't used because of worries of breaking it -- the design of that machine
wasn't very good and it apparently has reliability issues.
paul