interesting find

From: Thilo Schmidt <thilo.schmidt_at_unix-ag.uni-siegen.de>
Date: Thu Feb 6 21:54:56 2003

On 06-Feb-2003 Rick Bensene wrote:
> I have a strong feeling that this is a ROM rather than RAM.
> The rods form the core of a transformer. A bunch of 'word' wires
> each have a few turns wrapped around the (probably
> a ferrite material) rod in a clockwise or counter-clockwise to encode a
> 1 or a 0. Another winding around the rod is the sense coil. When a
> current pulse passes through one of the word wires, a current is induced
> into the sense winding. The induced current in the sense winding is
> different, depending on which way the word wire was wrapped around the
> rod. The current pulse in the sense winding is amplified and
> discriminated (to 1 or 0), and presented as the output for that bit.

Ahh, thanks that was the answer I was looking for... :-)
This would explain why the coils are mounted on removable "cards" inside
the module.

> A number of similar architectures were were commonly used for read-only
> microcode storage on computers and even calculators
> until the mid-1970's, when IC-based ROM began to appear.
And when nobody cared about the size, weight and power consumption
of computers... ;-)
 
> The HP 9100A/B calculators use a similar architecture, using
> wire bobbins instead of rods, for a microsequence store.
> The Wang 500, 600, and 700-series calculators also use a similar
> architecture, utilizing "U"-shaped ferrite structures as the transformer
> core, for microcode storage.

Now I remember reading an article that mentioned this type of memory.
The article was about radiation-hard memory used on early space
missions.

> Definitely a neat old relic.
Yeah, another interesting item for my collection of forgotten
memory technology :-)


bye

        Thilo
Received on Thu Feb 06 2003 - 21:54:56 GMT