How scarce (valuable) is core for the PDP-8?

From: Dave Dameron <ddameron_at_earthlink.net>
Date: Tue Apr 20 17:41:30 1999

At 03:28 PM 4/20/99 -0400, Allison wrote:

>Correct, but the pulse that indicates the core switched is delayed in
>time Hence the critical slice time. Core size affects this as does
>the select current.
>
>> Rather than using steel nuts - which may be very inconsistent in their
magnetic
>> properties - would ferrite beads, as used for interference suppression,
work?
>> Or to they have too small a hysteresis like transformer steel?
>
>Actually the nuts have an adaquate hysteresis to make a demo core but it
>would not work useably well. Ferrites used for beads have low
>permability. But since they are available I'd try one and see.
>
>> Nice Description, Allison. I like it.
>
>Core is mysterious but when broken down the mechanism is easy enough to
>understand. then you need to understand the interactions... ;)

Neat. I looked in my "junk" collection and found some cores.
One plastic box is labeled "Univac memory elements" and has a small sample
of 3 size cores. The largest is about 1mm O.D. and the smallest is less
than half that size. They look very fragile as the I.D. is almost as large
as the O.D.

The other is a "Indiana General 15 mill memory plane" I guess the cores are
15 mill diameter. There are 16 cores wired as a 4x4 plane. The wires are
much smaller than 30 SWG (about 28 AWG). I would say much smaller than 50
(either) gauge, I need a magnifier just to see them.

I didn't realize I had them, but this thread made me think of wiring a
small demo plane (another project).
-Dave

>
>Allison
>
>
>
>
Received on Tue Apr 20 1999 - 17:41:30 BST