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Old 7th Jan 2019, 2:14 am   #14
Karen O
Rest in Peace
 
Join Date: Jul 2011
Location: Bridgnorth, Shropshire, UK.
Posts: 787
Default Re: Retro computer homebrew: Orton Karenbak-1 computer

I did look into using LC delay lines. These were used in some valve calculators to store a single number. The trouble is you need 3 or 4 LC elements for every bit you want to store. Also, the circulating signal has to be amplified and reconditioned every 12 or so elements.

Actually Dominic, a 3.5" floppy would only have to spin at a little over 300rpm (i.e. normal speed) to provide a 5msec delay, provided I used a dual head of the sort used in cassette decks with off-tape monitoring. It's worth considering! A stereo head would also afford a clock channel which would ease the data recovery task.

Thank you for your kind comments Argus25. You know the feeling when you suspect something is possible...? I just had to build it to find out!

The Karenbak-1 NEARLY worked first time, but the problem wasn't the logic. The multi-position switch I chose was make-before-break, and this shorted my 5V supply! Adding pull-ups on the high-tied connections fixed that, and it worked exactly as planned after that.
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