Re: 6502, 65816 = RISC ?

[wbaguhn@nyx10.cs.du.edu (Will Baguhn)]

In article <4v1ddr$7fd@darla.visi.com>, Nathan Mates <nathan@visi.com> wrote:

>RISC means:
>
>1) Reduced instruction set. If you can do it with a few other
>instructions, that instruction shouldn't be there. (e.g. increment/
>decrement vs add/subtract of 1). 6502 fails.
>
>2) Lots of registers, usually 16 or 32. 6502 has 3 that are useful.
>Fails.
>
>3) You can do the same operations (add, subtract) to any register.
>6502 fails.
>
>4) [Optional, but it's been a hallmark of pretty much all commercial
>RISC chips] Pipelined execution. 6502 fails.
>
>5) [Even more optional] Integer multiplication on chip. 6502 fails.
>
>6) Designed with the RISC philosophy in mind. 6502 fails. [RISC wasn't
>even around at the time]
>
>   According to the technical definitions, the 6502 is NOT a RISC
>chip. It may be close and a good attempt, but it is NOT one.

AMEN.  If anything, RISC was designed after 6502 philosophy rather than
vice-versa.  (Let's face it: 6502 kicks pants off 8088 and friends; it's
simpler and it does the simple things more quickly than the 8088 
does.  You don't need string operations at the processor level.  You
don't need a lot of complicated things being done at the machine
code level.  You can get by just fine without multiply and divide
instructions, too (but leave the ASL and LSR's!  we need our doubles
and halves!).  I think that the 6502 sort of shook the computer
world with the revelation that a simple processor can be amazingly
powerful.  (comparison: I've got a VAX-11 programming card in front
of me.  It's a 58 page booklet to list out the data formats and
opcodes for a VAX-11 ("PDP-11 with Virtual Address eXtension") processor.)

And of course, thanks to the "rules" of computers, anything one computer
can do, any other computer can do.  A VAX can crunch numbers, my GS can
crunch numbers.  A VAX can do typesetting, my GS can do typesetting.
Heck, my GS can raytrace even.  All because of a simple processor
with no inherent memory management or a numerics module.

Yah, that'd shake up the computer world a little.  :)

>   If you believe everything you read online, I've got some good
>swampland^H^H^H^H^H^H^H^H^H real estate to sell you. Real cheap.
>
>Nathan Mates
>--
><*> Nathan Mates http://www.visi.com/~nathan/      <*>
># What are the facts? Again and again and again-- what are the _facts_?
># Shun wishful thinking, avoid opinion, care not what the neighbors
># think-- what are the facts, and to how many decimal places?  -R.A. Heinlein


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