Bernd, I knew of the RS/6000 and RISC but not that it was prevalent or original on the IBM mainframes.
Scott ford www.identityforge.com Tell me and I'll forget; show me and I may remember; involve me and I'll understand. - Chinese Proverb On Feb 17, 2013, at 4:03 AM, Bernd Oppolzer <[email protected]> wrote: > I'd like to second that, for some reasons: > > a) other machines like RS/6000 etc borrowed the RR/RX/RS instruction set > from the S/370, and they are RISC in my opinion > > b) I know other machines (old German mainframes) which are definitely CISC, > and they have stack instructions or they are able to modify other > instructions > by combining them with stack instructions and replacing the address part of > the instructions by register references and all such things - that is > really complicated - > compared to that, the S/370 instruction set is very simple. You can do > very much > with only one instruction of the TR 440 mainframe ... increment a register, > store into a memory location ... all in one combined instruction, which you > can compose of two simple instructions etc. > > c) think of the pipelining efforts the modern z processors do - that's > RISC - > up to ten instructions executing in parallel > > As Tony said: the complex instructions like EDMK only count for a very small > percentage in the executed instructions summary. > > The mainframe, in fact, is both: a very fast RISC processor, and a > decimal machine, > doing commercial workload at a reasonable speed. > > Kind regards > > Bernd > > > > Am 17.02.2013 01:17, schrieb Tony Harminc: >> On 15 February 2013 21:33, Robin Vowels <[email protected]> wrote: > > > >> The S/360 is clearly definitely and unequivocably a CISC machine. > >> Think of instructions like ED, EDMK, TR, TRT, PACK, UNPK, CVB, CVD, > >> and of course all the decimal arithmetic instructions, all the > >> character move and compare instructions (except the immediate > >> instructions). Then there are the shift instructions, whose times > >> depend on the number of positions to be shifted; the > >> floating-point instructions, which pre- and/or post-normalize > >> (except for Halve); multiply and divide instructions. Then for the > >> S/370, instructions like MVCL and CLCL were added. > > > > One might better think of the mix of instruction encountered in a > > real world instruction stream. ED and EDMK form a minuscule fraction > > of all instructions executed, and even in a commercial environment, > > the packed decimal instructions (including CVB, CVD, PACK, and UNPK) > > form a very small portion. Indeed only the RR and RX instructions > > (and their modern counterparts) show up on any sort of ordinary > > graph of instruction use, and all others can go in the "other" > > bucket. > > > > Certainly S/360 and S/370 are CISC machines from a time long > > predating the terms RISC and CISC. But for practical purposes (such > > as compiler writing or performance analysis) rather than academic > > taxonomy, they may as well be RISC. > > > > Tony H. > >
