What are the really unusual or weird computers?

How about , the 3 Rivers PERQ. OK, it _could_ be a unix box (but with a GUI before such things were at all common). It also ran an OS called POS written in Pascal. The user interface is somewhat similar to, say, RT11, though. What makes the PERQ odd is the processor. Yes, it's von Neumann. It has 256 general-pupose registers, with (in later versions) an index register to address the registers (!). The microcode which determines the instruction set is not stored in ROM, but in RAM, and is loaded from disk when the machine boots. Difference OSes had different microcode, and you (the user) were expected to write your own microcode, at least under POS. Oh, and the CPU registers/ALU are 20 bits wide (24 bits in the T4), which is unusual. Another odd thing for the time is that there was no text mode on the display. Only a bitmapped graphics mode. There was a graphics accelerator on the CPU board (the so-called 'rasterop machine') to move bitmaps around, and which caued this machine to have a text display rate much faster than the typical serial terminals of the time. That was, I am told, a design spec They're not that rare (in that several people here have them, I think), but they're interesting. I should perhapc qualifiy that by saying the T4 (24 bit model) _is_ seriously rare. -tony