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

From: Dave Dameron <ddameron_at_earthlink.net>
Date: Thu Apr 22 08:10:39 1999

At 08:49 AM 4/22/99 -0400, Allison wrote:
>> >Cores large enough for visual indication of magnetic field would be in the
>> >10-20AMPS select curent range. Not a real possibility.
>>
>> Maybe so, but those are practicality issues, not feasibility.
>
>that answer equates to "whatever". Describe the mechanics of displaying
>the orientation of a magnetic field in a closed torus? I was trying to
>get someone to think on how thjis may be done impractical or not.
>
Yea, the field lines are contained inside the toroid, no external poles.
For an *exotic* way, the
Aharonov-Bohm effect might work. See the Scientific American article, April
1989. This, by the way, is that the magnetic potential is outside the torus
and can effect an electron in the quantum realm. Of course the effort and
equipment to do this for 1 bit would overwhelm the rest of the machine!
More on topic, the magnetic cores they used were 5 microns in diameter and
ferromagnetic, not "ferroelectric". They were 83% Ni and 17% iron, on a
silicon wafer, also shielded by niobium.
-Dave
Received on Thu Apr 22 1999 - 08:10:39 BST