Path: utzoo!utgpu!attcan!uunet!husc6!bloom-beacon!gatech!rutgers!bellcore!tness7!tness1!sugar!ficc!peter
From: peter@ficc.UUCP (Peter da Silva)
Newsgroups: comp.arch
Subject: Re: dedicated vs general-purpose CPUs
Message-ID: <1221@ficc.UUCP>
Date: 5 Aug 88 14:04:21 GMT
References: <5254@june.cs.washington.edu> <76700032@p.cs.uiuc.edu> <1988Aug3.180947.12070@utzoo.uucp>
Organization: SCADA
Lines: 39

In article ... henry@utzoo.uucp (Henry Spencer) writes:
> But phrase it another way:
> do you want your CPU power in one block that you can allocate as you please,
> or divided up into fixed-size chunks, most of which are not under your
> control?

As big a block as possible. Unfortunately in the real world cheap computers
(such as Amigas or Suns or IRISes) have to use prepackaged parts: 68000s,
or 68020s, or 68030s, or 80386es, or SPARCs, or 88000s, or...

So, you *have* to use fixed size blocks. Once you have pulled all the
power you can out of your 680x0 or RISC chip, and you need more MIPS,
you have to add more processors. So, you have the graphics (and serial-IO
and disk IO and any other IO you care to name) wheel of life.

The other alternative is to build your own custom minicomputer or mainframe
with a single processor that gives you a zillion MIPS in one package. I
think you have already shot down that idea by pointing out that general
purpose processors will overtake you. I worry about SUN and SPARC in this
context...

Better to use a GP processor as your main CPU, and use a graphics library
that's implemented in hardware or software, whichever's cheaper. When you
run out of MIPS, stick a graphics accelerator (like the Amiga Blitter)
in and pop in a new shared library. When you get a bigger CPU, go back to
your software-only library. Or write a new one that uses the new 68040
instructions.

The most bang for your buck. Forever.

-- 
PS: The Amiga Blitter is mostly accessed through libraries. So when the
680x0 becomes faster than the blitter you can just change graphics.library.
Don't even have to recompile.
-- 
Peter da Silva, Ferranti International Controls Corporation, sugar!ficc!peter.
"You made a TIME MACHINE out of a VOLKSWAGEN BEETLE?"
"Well, I couldn't afford another deLorean."
"But how do you ever get it up to 88 miles per hour????"