[cctalk] Re: Intel 4004(sp?)

Which might explain why the x86 ISA is such a convoluted tangle. Moto did those things too in various places, though: consider the 68k family. The 68040 is clearly a derivative design but with a pile of things added. Come to think of it, creating an ISA once and extending it N times is standard industry practice, from PDP11 to VAX to Alpha to MIPS to Power, not to mention earlier examples like CDC 6000/170/180 series, various IBM families, Electrologica... I'd say it is probably harder to come up with singleton designs, especially several of them from a single company, than families. The value of N tends to depend on how well conceived the original architecture is (which is why N is smaller for PDP11 and VAX and MIPS than it is for x86) and also on the longevity of the family. So while Intel made a very large family starting with the 4004, they made very small families out of the i960, iAPX432, and various others. paul