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Simulating the IBM 360/50 Mainframe From Its Microcode

submitted by auto_turret__rev_A to Mildlyinteresting 2.3 yearsFeb 2, 2022 06:03:01 ago (+3/-1)     (Mildlyinteresting)

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Can't submit link post yet, not enough popularity points.

Check out that 17,600 bit memory that holds the machine's microcode, called "BCROS" (balanced capacitor read-only store). It's essentially a copper sheet with the bits etched into it.

If I manage to stick around long enough, going to have to start an apathetically modded vintage tech sub.


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[ - ] gimpyoldman 1 point 2.3 yearsFeb 2, 2022 10:52:15 ago (+1/-0)

In 1969 I went thru electronic and computer training in the military. the first mainframe I worked on had vacuum tubes in the power supply. We used to sit on it to stay warm.

[ - ] localsal 1 point 2.3 yearsFeb 2, 2022 07:04:45 ago (+1/-0)

Very nice.

Do you have any info on the IBM research lab that was working on voltage vs current bits?

As in, instead of ram being a stored voltage in a capacitor, it was a stored current in an inductor.

I heard a story long ago (some retired guy) about how they almost got low loss inductors to be a thing.

[ - ] auto_turret__rev_A [op] 1 point 2.3 yearsFeb 2, 2022 07:25:58 ago (+1/-0)

Closest thing I know of is core memory, where the bits are stored in a matrix of ferrite rings whose magnetic field orientation represents the 0's and 1's. If you hear anything more about it, let me know.

[ - ] localsal 1 point 2.3 yearsFeb 2, 2022 07:42:10 ago (+1/-0)

I heard this years ago from a guy that retired from IBM in the mid/late 80s - so all second hand. It could be what you describe.

[ - ] auto_turret__rev_A [op] 0 points 2.3 yearsFeb 2, 2022 07:44:07 ago (+0/-0)

Those things were woven by hand, insane.

[ - ] gimpyoldman 1 point 2.3 yearsFeb 2, 2022 11:00:27 ago (+1/-0)

This, one of the first main frames I worked on was the UNIVAC CP 808. It had vacuum tubes in the power supply and core memory. We had a core failure (actually on bit at one address was always on) in the system I was working on at an overseas base. Tried to order a replacement core stack. But too much $$$. They didn't believe me that it could not be repaired on-site. They requested a field engineer from the factory be sent over, I told him what I had found, he ran the same test I did and 5 minutes later told my military bosses 'you need a new core stack'.

[ - ] FacelessOne 1 point 2.3 yearsFeb 2, 2022 06:11:12 ago (+1/-0)

NERD!