Re: [TUHS] core

[Doug McIlroy <doug@cs.dartmouth.edu>]

Tim Bradshaw wrote:
"Making tube (valve) machines reliable was something originally sorted out by Tommy Flowers, who understood, and convinced people with some difficulty I think, that you could make a machine with one or two thousand valves (1,600 for Mk 1, 2,400 for Mk 2) reliable enough to use, and then produced ten or eleven Colossi from 1943 on which were used to great effect in.  So by the time of Whirlwind it was presumably well-understood that this was possible."

"Colossus: The Secrest of Bletchley Park's Codebreaking Computers"
by Copeland et al has little to say about reliability. But one
ex-operator remarks, "Often the machine broke down."

Whether it was the (significant) mechanical part or the electronics
that typically broke is unclear. Failures in a machine that's always
doing the same thing are easier to detect quickly than failures in
a mchine that has a varied load. Also the task at hand could fail
for many other reasons (e.g. mistranscribed messages) so there was
no presumption of correctness of results--that was determined by
reading the decrypted messages.  So I think it's a stretch to
argue that reliability was known to be a manageable issue.

Doug