Tru64 and the DECSYSTEM 20 1079

One way to look at the difference is that for the Mac, CISC support was accomplished by adding a layer of emulation for CISC software on RISC hardware; while with the 400, the emulation layer was already there in the CISC machines, so the transition to RISC didn't involve adding one. So the transition was somewhat easier in the 400's case.

The 400 transition wasn't *completely* seamless. It's possible to create programs on a CISC AS-400 that can't be installed on a RISC AS-400, though I think the default is to build program objects on CISC with "visibility" so they can be moved to RISC. It was very smooth, though, and most users and developers probably never saw any difference. Even for most system administrators the change was pretty minor, I suspect. (It was for us, and we were writing commercial AS-400 system-level software, insofar as you can do that on the '400 without working for IBM, that had to support both CISC and RISC, so we had one of each.)

Apple did an excellent job with the transition. I think it's their most impressive technical and marketing feat, actually - more than the original Apple or the original Mac.

--

Reversible CA's are -automorphisms- on shift spaces. It is a notorious fact in symbolic dynamics that describing such things on a shift of finite type are -fiendishly- difficult. -- Chris Hillman