The early microcomputers (8008, 6800, 6502) are actually a lot more like the PDP-8 than the PDP-11: a single (or possibly double) accumulator register and a few special purpose registers hardwired to various instructions. The 68000, Z8000 and NS16032 were the first true successors of the PDP-11, sharing (to an extent) the unique characteristics of it's design with general purpose registers (with even SP and PC being general purpose registers with only very little magic attached to them) and an orthogonal design. The 68000 still had lots of little quirks in the instruction set, the latter two actually improved on the PDP-11 set (where a couple of instructions like XOR would only work with register-destination because it was added to the design in a stage where there weren't enough bits left in the instruction space, I guess). And the 8086 was just a souped-up 8080/8008: each register had a different function, no orthogonality, etc. Intel didn't get it "right" until the 386 32-bit instruction set (and even there some of the old baggage can still be seen). -- Jack Jansen | ++++ stop the execution of Mumia Abu-Jamal ++++ Jack.Jansen@oratrix.com | ++++ if you agree copy these lines to your sig ++++ www.oratrix.nl/~jack | see http://www.xs4all.nl/~tank/spg-l/sigaction.htm