Hi Ben I didn't build it, I just made it work. A real pain, since I didn't have any schematics and it had several problems. There are a couple of pictures at: http://www.rdrop.com/~jimw/jcgm-vcfiv.shtml Look down 8 rows. The first 2 pictures in that row are my Nicolet machine ( It has 12Kx20 core ). It is all ttl/dtl, thought. Notice the front panel switch position. It is 7600 octal, the boot vector in core. One of the interesting things is the ALU. It has a 5 input port adder. One can select from, ALU, ALU*, MEM, MEM* and "one" to add together. One can do a lot with this combination. Anyway, back on the original subject, there are also some interesting minimal instruction processors described out there. As I recall, there was one that had only 4 operations. SUBtract was one of them ( considered more important than an ADD ). I've been toying with making a single bit relay based computer. My intent is to make the main memory bank using reed relays with a magnet to bias them. The idea is that the external magnet has just enough effect that if the reed relay is closed, it stays that way. If it is opened it stays open. One would arrange these relays in an array with small ceramic magnets, north and south poles alternating so that there is no cumulative bias. Writing to the reeds, coil in opposite directions causes it to open or close. Data is handled by a shift register so that the bus is always 1 bit wide. It'll be slow but what the heck. To make things a little more complicated, I expect to use 3 phase clocking. With this, I can use overlapped clocks, without racing. Dwight