
The core memory inside a Saturn V rocket's computer - matt_d
http://www.righto.com/2020/03/the-core-memory-inside-saturn-v-rockets.html
======
DennisP
My dad used to work as a customer engineer for IBM. When I was about seven
years old he took me to work, and showed me the printing press and mainframe
at the Washington Post. He opened up a cabinet and there was the core memory
with its thousands of crisscrossing wires. Now when I look at a multi-gigabyte
chip, I still occasionally think of the time I could see a little donut for
every bit.

------
LeoPanthera
An often forgotten fact is that core memory is why a "core dump" is called
that.

Core memory isn't wiped on loss of power, so you could read the contents out
of a dead machine, to see the last state.

~~~
gumby
I used to program a KA-10 (one of the main primary research architectures of
the ARPANET -- ask yourself why Berkley sockets work the way they do). Anyway
it had core memory except for the machine registers which were semiconductors
(DTL, not TTL). Those 16 machine registers were also the first 16 addresses in
memory BTW.

Aaaanyway, the power in Cambridge would sometimes go out, and when it did
whatever process was running would die, as all the register state (including
PC which was a separate register) would be lost. But otherwise you could just
restart since the core was fine. Of course if the monitor (i.e. kernel in
today's parlance) was running, well you were sunk.

~~~
mmoez
> ask yourself why Berkley sockets work the way they do

Interesting... Is it possible to shed some light on how Berkley sockets were
influenced by that architecture?

------
chmaynard
"The contents of core memory are retained when the power is disconnected, so
it's likely that the module still holds the software from when the computer
was last used, even decades later."

A useful feature if the vehicle containing the module is involved in an
accident and ends up on the ocean floor. A successful core dump would reveal
the state of main memory at the instant power was lost.

~~~
woofyman
I use to program the F-15 central computer. One went down in Alaska. The
computer was underwater for 2 weeks. Once retrieved, we washed the core memory
boards in distilled water. We were able to determine the state of the jet when
it lost power.

~~~
kens
Did the F-15 use an IBM 4π computer or something else? What language did you
use to program it. (I think aerospace computers are underappreciated, so I'm
interested in whatever you can tell me about it.)

~~~
thetrumanshow
That information may be sensitive. The F-15 platform is still under active
development, and even if it wasn't those details might be too much to ask.

------
madengr
My company still builds core memory for a military flight computer. It’s
cheaper than re-qualifying a new computer.

~~~
kens
I'd be interested in knowing what core memory computers are still in use, if
it's not secret.

------
4x5-Guy
I started working at Burroughs in 77 as a field engineer. We still had one or
two tube/core based computers out at customers sites. Just amazed me at the
time when I got to see them. I never got to work on them, I started with the
systems built with dtl chips. Memory was 1k x 1bit chips.

The good old days...

------
ThisIsTheWay
There is a great Linus Tech Tips and Smarter Every Day Youtube video about
this. Highly recommended!

[https://www.youtube.com/watch?v=olRF5Ckaga0](https://www.youtube.com/watch?v=olRF5Ckaga0)

~~~
sixothree
Ever since I learned Destin from Smarter Every Day works in defense I have
lost interest in his channel. That was a disappointing discovery, though I did
suspect it.

~~~
205guy
Upvoted you because I got turned off his channel by a similar but different
issue last year: firearms.

He was doing a lot of episodes involving rifles, such as viewing the bullet's
turbulence with polarization (iirc) and slo-mo. It was still scientific, but
just a lot about guns. Then in the intro to one episode (sorry, I can't be
bothered to go reference all of these), he said something like: people have
criticized me because I talk a lot guns, but they're just so cool. In other
words, "sorry not sorry." I closed the tab and never went back to his channel.

I'm in the US and I know guns are mainstream in the US, and he was actually
good at studying them (not even really glorifying them). But there had been a
lot of high profile shootings (Sandy Hook, Las Vegas, Florida, etc.), so it
just seemed off. And frankly, I'm not into guns myself (just like I'm not into
the foodie trend), so since he stated clearly he was going to focus on
firearms, I just stopped following.

It's a youtube channel, and we all have limited time, so I see nothing wrong
with stating a reason for giving up on it--even if it's a politically or
culturally charged issue. It's not like the parent comment or I are
criticizing the channel or even arguing he shouldn't do what he does.

~~~
scottLobster
They kinda are though.., or at least it's the most obvious implication. The
entire comment is them saying they stopped watching after finding out he
worked in the defense industry. Nothing to do with the content of the linked
video, nothing to do with the original article. Just a statement that they
think working in the defense industry is bad enough to stop watching the
channel. If they aren't implying that we shouldn't watch SmarterEveryDay
because of his career background, then they should have more clearly stated
their point. As it stands the comment sounds like the classic "phrase a
controversial point as an obvious implication so when people call you out on
it you can backtrack and say they misinterpreted".

------
ralphc
In the 80's I went to a college's "yard sale" and picked up a HP 9100B
programmable calculator; they have core memory. When I plugged it in I
remember it starting to run the program it had in it, not missing a beat. I
still have it, maybe it's time to see if it still works.

