small valves

[Bjørn Vermo]

On 23 May, 2005, at 09:20, Tom Jennings wrote:
>
> Successful commercial core memories require grossly underpaid
> philipino housewives or other exploitable labor; welcome to the
> fruits of capitalism.

At the end of the core era (or maybe a little after the end), NCR used 
"knitting machines" to make core planes.
They even had an accounting machine where the entire logic was core 
based (inhibit core was their name for the technology).

The last magnetic memory (I think) for the NCR Century was "plated 
wire". They used cobalt-plated wires instead of rings, it was much 
easier to manufacture but the S/N ratio on the read wire was terrible.

NCR was much into cobalt, they also used cobalt-plated disks instead of 
the usual iron oxide coatings of the day for some high-end drives. The 
disks were shiny blueish black.

If you just want to play and make a 4 x 4 core or something, I
> wonder if you couldn't get decent hysteresis with some other
> ferrite product. You could compensate for a "poor" core with good
> electronics and/or brute force. I haven't looked at a toroid spec
> sheet in ages and not for hysteresis.

My guess is that the ferrite rings made by TDK for noise suppression 
should work OK. They will obviously be lossy (they are designed to be), 
but they should have fairly high hysteresis. As long as you do not work 
them too hard, they should not get hotter than a P4 Prescott :-)

-- 
-bv