rogues galleries

Basically, they're TV-scan-rate image displays for minicomputers. I have Unibus interfaces for mine, but the schematics also include diagrams for DG Nova and HP2100 interfaces IIRC. The basic idea is a number of byteplanes, each 512*512*8 bits. The outputs of these go to (programmable) look-up tables, then to a full adder, then to more look-up tables, then to DACs (either 3 * 8 bit or 3 * 10 bit). By careful programming of the lookup tables you can obvious add the values in the byteplanes, subtract them (program a 2's complement table), multiply (program log/antilog tables) and so on. And there's more. Firstly there's a hardware histogram board which produces a historgram of the pixel values in a byteplane (I think, maybe the outputs of the adder), and lets the host computer read it out. There's the 'transform ALU' which treats planes 0 and 1 as a 16 bit accumulator, and lets you combine that with any other plane using any function a 74181 ALU chip can perform. And there's a cursor, moveable by a graphics tablet or trackball. And overlay bitplanes for text/labels. I own 3 of these machines. The 70/E is in 3 rack crates (processor and 2 memory crates). It uses 4K bit DRAMs (over 3000 of them), and has a total of 6 planes. The 74/F4 uses 16Kbit DRAMs, has 4 planes, and fits into 1 crate. The Model 75 is a later unit, using 64K DRAMs, and has some other features like a small (empty) Multibus cage for a local CPU, and a 'transform sequener' -- a 2910 sequener chip + control store RAM which lets toy user-microprogram the thing to do automatic sequences of operations. Needless to say this is not a simple machine. It's many boards of fairly simple ICs. -tony