IBM 1620

Chuck Guzis cclist at
Sun Aug 30 13:34:38 CDT 2015

On 08/30/2015 11:15 AM, Paul Koning wrote:

> So there'd be what, 120,000 cores to thread?  That might be a bit
> daunting from a human-hour standpoint.  I'll wager that 120K cores
> wasn't even a day's output for outfits like Fabritek.
> Those cores weren't threaded one by one.  You'd start by setting the
> cores into a holding jig, which positions them correctly.  Then you
> thread wire from edge to edge.  The article mentions a needle with
> the wire welded to its end; that makes sense because the copper wire
> is unlikely to be stiff enough.  So the number of individual
> threading operations is 3-4x the square root of the core plane size.
> For example, on a 4k core plane, it would be 200 steps, give or take.
> (A bit more on a CDC 6000 series core plane with its peculiar 5 wire
> architecture.)

I've seen the archival photos.  Still, the possibility of missing or 
damaging a single core was always there.   I wonder what the rejection 
rate was.

I have heard of machine-fabricated core as well, but I thought that it 
only applied to larger, slower bulk core store.  One can certainly 
understand why plated-wire or thin-film technologies were attractive.

Sigh.  Another lost manual art.  I can remember during the 70s that the 
hot thing was to learn IC layout--the wives of a number of co-workers 
were going to night courses for that.


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