> >> One of the things I have noticed is that great similarity exists between a
> >> couple of instruction sets, the 6502 and the Sparc, and the IBM 360 and
> >> 68000. Kind of the classics of RISC and CISC, and I love them both.
> >Um, what are you smoking, and where can I get some? :-)
> >Having programmed all four of those processors, I would not be willing
> >to concede much similarity between any two of the four.
> Maybe you forgot to enhale,
Could this be a common problem over at your side of the pond ?
> there aren't more than a handfull of different
> instructions between the pairs I mention. I haven't programmed the Sparc,
> but I did spend about two weeks testing the feasibility of porting a 65C02
> assembly language program to the Sparc, and it looked very very good.
I did a port of an 8080 code fragment to a /370 class CPU, and it
also looked quite good and straight foreward, althrough there is
no simirarity between the CPUs at all - so where is the point ?
I'm not 100% shure for the SPARC, but AFAIK it, there are no
similarities beyound anything common to most processors.
The same is especialy true for the 68K/360 pair - just to start with
one of the most important features of the 68K: Addressing modes -
the 360 got just ONE (base+offset[+index]) not to mention increment
or decrement instructions at all. And of course as a result no stack!
Hey, nothing against the /360/370 system I found that this singe
addressing mode is flexible enough to get any result needed as easy
as with an 68K processor with his dozens or so modi - but just not
compatible in any way.
> As
> for the 360/68k, IBM made a varient of the 68k that ran 360 code native.
Thats not an argument for either side, I don't know the IBM solution,
but in the mid 80s SIEMENS got a similar machine, the PC-2000 (a
NSC 16016 Multibus Unix system with a /370ish board), based on a
68020 with new microcode to emulate a X4 like CPU (a /370 compatible
CPU from SIEMENS with a lot of enhancements, like bit field operations
or a some stack like instructions (no, no push or pop, but rather
some kind of queuemanagement to enqueue and dequeue structures and
follow (almost) unlimited levels of indirection)). But this machine
was no longer any 68K - just the silicon has been the same.
So, where is your point of similarity ?
Gruss
H.
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Ich denke, also bin ich, also gut
HRK
Received on Fri Apr 16 1999 - 16:31:22 BST