If I read the wikipedia entry for Whirlwind correctly (not a safe
assumption), it was tube based, and I think there was a tradeoff of speed,
as determined by power, and tube longevity. Given the purpose, early
warning of air attack, speed was vital, but so, too, was keeping it alive.
So a means of finding a "sweet spot" was really a matter of national
security. I can understand Forrester's pride in that context.

On Tue, Jun 19, 2018 at 8:58 AM, Clem Cole <clemc@ccc.com> wrote:

>
>
> On Tue, Jun 19, 2018 at 8:23 AM, Noel Chiappa <jnc@mercury.lcs.mit.edu>
> wrote:
>
>>     > From: Doug McIlroy <doug@cs.dartmouth.edu>
>>
>>     > Yet late in his life Forrester told me that the Whirlwind-connected
>>     > invention he was most proud of was marginal testing
>>
>> Given the above, I'm totally gobsmacked to hear that. Margin testing was
>> important, yes, but not even remotely on the same quantum level as core.
>
> ​Wow -- I had exactly the same reaction.     To me, core was the second
> most important invention (semiconductors switching being he first) for
> making computing practical.   I was thinking that systems must have been
> really bad (worse than I knew) from a reliability stand point if he put
> marginal testing up there as more important than core.
>
> Like you, I thought core memory was pretty darned important.  I never used
> a system that had Williams tubes, although we had one in storage so I knew
> what it looked like and knew how much more 'dense' core was compared to
> it.   Which is pretty amazing still compare today.  For the modern user,
> the IBM 360 a 1M core box (which we had 4) was made up of  4 19" relay
> racks, each was about 54" high and 24" deep.    If you go to
> CMU Computer Photos from Chris Hausler
> <http://www.silogic.com/Athena/CMU%20Photos%20from%20Chris%20Hausler.html>
> ​ and scroll down you can see some pictures of the old 360 (including a
> copy of me in them circa 75/76 in front of it) to gage the size).
>
>
>
> FWIW:
> I broke in with MECL which Motorola invented / developed for IBM for
> System 360 and it (and TTL) were the first logic families I learned with
> which to design.   I remember the margin pots on the front of the 360 that
> we used when we were trying to find weak gates, which happened about ones
> every 10 days.
>
> The interesting part to me is that I'm suspect the PDP-10's and the Univac
> 1108 broke as often as the 360 did, but I have fewer memories of chasing
> problems with them.   Probably because it was a less of an issue that was
> causing so many people to be disrupted by the 'down' time.
> ᐧ
>