19 Jun
2018
19 Jun
'18
12:23 p.m.
From: Doug McIlroy <doug(a)cs.dartmouth.edu>
Core memory wiped out competing technologies (Williams
tube, mercury
delay line, etc) almost instantly and ruled for over twent years.
I never lived through that era, but reading about it, I'm not sure people now
can really fathom just how big a step forward core was - how expensive, bulky,
flaky, low-capacity, etc, etc prior main memory technologies were.
In other words, there's a reason they were all dropped like hot potatoes in
favour of core - which, looked at from our DRAM-era perspective, seems
quaintly dinosaurian. Individual pieces of hardware you can actually _see_
with the naked eye, for _each_ bit? But that should give some idea of how much
worse everything before it was, that it killed them all off so quickly!
There's simply no question that without core, computers would not have
advanced (in use, societal importance, technical depth, etc) at the speed they
did without core. It was one of the most consequential steps in the
development of computers to what they are today: up there with transistors,
ICs, DRAM and microprocessors.
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.
In trying to understand why he said that, I can only suppose that he felt that
core was 'the work of many hands', which it was (see e.g. "Memories That
Shaped an Industry", pg. 212, and the things referred to there), and so he
only deserved a share of the credit for it.
Is there any other explanation? Did he go into any depth as to _why_ he felt
that way?
Noel
19 Jun
19 Jun
12:58 p.m.
New subject: core
On Tue, Jun 19, 2018 at 8:23 AM, Noel Chiappa <jnc(a)mercury.lcs.mit.edu>
wrote:
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
From: Doug
McIlroy <doug(a)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. 
1:53 p.m.
New subject: core
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(a)ccc.com> wrote:
On Tue, Jun 19, 2018 at 8:23 AM, Noel Chiappa <jnc(a)mercury.lcs.mit.edu>
wrote:
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
From:
Doug McIlroy <doug(a)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. 
21 Jun
21 Jun
2:09 p.m.
New subject: core
On 6/19/18, Noel Chiappa <jnc(a)mercury.lcs.mit.edu> wrote:
In other words, there's a reason they were all dropped like hot potatoes in
favour of core - which, looked at from our DRAM-era perspective, seems
quaintly dinosaurian. Individual pieces of hardware you can actually _see_
with the naked eye, for _each_ bit? But that should give some idea of how
much
worse everything before it was, that it killed them all off so quickly!
When we replaced our S/360 model 25 with a S/370 model 125, I remember
being shocked when I found out that the semiconductor memory on the
125 was volatile. You mean we're going to have to reload the OS every
time we power the machine off? Yuck!!
-Paul W.
2129
days inactive
2131
days old
3 comments
4 participants
participants (4)
-
Clem Cole -
jnc＠mercury.lcs.mit.edu -
John P. Linderman -
Paul Winalski