Info about a Mullard Core

Rod Smallwood RodSmallwood at
Sun Nov 4 13:56:32 CST 2007

I used to work on similar Mullard core stores. 
They where part of the memory units in 4100 mainframes. 
The ones I knew where definatly 4K (4096). 
They were mounted in the centre of a card rack with read/ write boards
on either.
OC81 and OC71 transistors in great profusion. 
Some had to be gain matched. You started with a box of 500 OC81's, a
pile of paper cups
 and a transistor tester set to measure hfe.

Rod Smallwood


-----Original Message-----
From: cctech-bounces at
[mailto:cctech-bounces at] On Behalf Of Roger Holmes
Sent: 01 November 2007 00:38
To: cctalk at
Subject: Re: Info about a Mullard Core


> From: "Gavin Melville" <gavin.melville at>
> Subject: Info about a Mullard Core

> Hi,
> I have had for many years a large core, and while I don't really want 
> to part with it, I also see what little pieces of core sell for on 
> ebay....
> I was told when given this about 15 years ago that it was from a 
> Burroughs mainframe which was installed at the Cadburys head office in

> New Zealand and that they had paid GBP 20,000 for it in 1960.

20,000 for the core or for the mainframe?

How sure are you about it being Burroughs? Wouldn't they be using U.S.
components rather than British?

I know Cadburys bought an ICT 1300 series machine around 1963/4, and its
now in a museum in NZ. It was a 48 bit machine, but I think it had a
much smaller store of 1200 or 2000 words and would have cost around
100,000 GBP. I have read there was an option to replace all the 'barn
door' core stores with a single store of 4,000 words of 48 bits, though
I've never seen one, nor the logic diagrams. I have always wondered
whether it used a full binary decode (using 16384 words to provide 4000
words of usable memory) of the 14 bits rather than a BCD decode. The
1300s use lots of Mullard components.

Just a small piece of a jigsaw puzzle, maybe not even the right puzzle!

Roger Holmes.
Owner of the last working ICT 1301.

>   I have
> been unable to find out if this was correct however.   Does anyone on
> the list know anything about it ?
> pictures at
> There are 921600 cores in the array, which is made up of 48x48 cores, 
> 4 to a layer and 100 layers.
> _________________________________
> Regards,
> Gavin Melville
> Senior Engineer
> Acclipse Electronic Ltd

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