Path: utzoo!attcan!uunet!samsung!uakari.primate.wisc.edu!ames!amdcad!weitek!weaver
From: weaver@weitek.WEITEK.COM
Newsgroups: comp.arch
Subject: Re: Magnetic amplifiers? [was Re: Mercury delay lines]
Message-ID: <25079@weitek.WEITEK.COM>
Date: 12 Jun 90 15:58:00 GMT
References: <2072@mindlink.UUCP>
Sender: weaver@weitek.WEITEK.COM
Reply-To: weaver@weitek.UUCP (Michael Weaver)
Organization: WEITEK Corp. Sunnyvale Ca.
Lines: 20

The magnetic amplifiers mentioned worked as follows: 
a strong clock pulse  and a synchronous weak data pulse 
are both fed into a magnetic core. If the sum of the currents
input are great enough, and opposing the current magnetic state
of the core, the core reverses magnetic polarity, and a magnetic
pulse is generated. A seperate output winding can be used to
pick up this output pulse. The output pulse can be more powerful
than the the data pulse, so the circuit is an amplifier.

An Wang, who founded Wang labs did a lot of work on this area 
(in the 40s (?)) before magnetic cores were found to be useful
for bulk memory, making logic gates and such.

The only commercial use I have heard of was in one of the first 
core memories sold by IBM. Large cores were used in a decoder
circuit to drive the memory plane. This reduced the tube count 
from (say) 32 to (say) 4.

I learned this John Pugh's "Memories that Shaped an Industry",
a book on core memories from by a former IBM engineer.