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 classiccmp.org [mailto:cctech-bounces at classiccmp.org] On Behalf Of Roger Holmes Sent: 01 November 2007 00:38 To: cctalk at classiccmp.org Subject: Re: Info about a Mullard Core Hi, 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.