Oppolzer - Informatik / Blog

I once looked at instructions generated by a PASCAL compiler for a RS/6000
machine and realized that I could read it, although I never learned anything
about the RS/6000. That's because the RS/6000 instruction set WAS INSPIRED BY
the S/360 instruction set, in my opinion. It was not a descendant of that
architecture or so. It was a complete different machine.

Kind regards

Bernd



Am 17.02.2013 15:36, schrieb S.F.:
> Bernd,
>
> I knew of the RS/6000 and RISC but not that it was prevalent or original
> on the IBM mainframes.
>
> S. F.
>
> 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 <bernd.oppolzer@t-online.de> 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 T. 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
>>
>>