Path: utzoo!utgpu!attcan!uunet!cbmvax!daveh
From: daveh@cbmvax.UUCP (Dave Haynie)
Newsgroups: comp.arch
Subject: Re: Blitters and design philosophy
Message-ID: <4462@cbmvax.UUCP>
Date: 10 Aug 88 17:11:00 GMT
References: <1988Aug1.062659.25971@utzoo.uucp>
Organization: Commodore Technology, West Chester, PA
Lines: 32

in article <1988Aug1.062659.25971@utzoo.uucp>, henry@utzoo.uucp (Henry Spencer) says:

> In article <401@ma.diab.se> pf@ma.UUCP (Per Fogelstr|m) writes:
>>... Do that with the CPU. Even with external hardware the CPU will not
>>be able to generate the addresses fast enough. (You have to generate a new
>>address each 50-100ns).

> Have you, pray tell, seen the manual for the AMD 29000?  I have.  Please
> read it before proclaiming this performance to be beyond that of a CPU.
> (The 29000 is available today, although it's not yet cheap.)  Or the
> manual of any modern RISC-based machine, for that matter.

Not even just in RISC chips, either.  This new 33MHz 68030 I just got in (also
not at all cheap) can run normal memory cycles in 60ns, burst cycles for cache
fills in 30ns.  That's certainly in the aforementioned ballpark.

Of course, this part is also very "not yet cheap".  It would make a killer
graphics engine, as would an AMD 29K or just about any CPU at that speed.  But
if you're going to that kind of high end to begin with, you can for the most
part get much better graphic performance out of some special purpose graphic
chip set like the National 8500 series.  For quite a bit less, too.  No reason
you can't make the host CPU a hot micro, and use it for anything that it can
do faster than the custom display processors.  But no matter how you slice it,
an 8500 system with 24 bitplanes is scrolling 24 planes in parallel, while the
'030 or 29K will have to scroll 24 planes one-at-a-time.  

> MSDOS is not dead, it just     |     Henry Spencer at U of Toronto Zoology
> smells that way.               | uunet!mnetor!utzoo!henry henry@zoo.toronto.edu
-- 
Dave Haynie  "The 32 Bit Guy"     Commodore-Amiga  "The Crew That Never Rests"
   {ihnp4|uunet|rutgers}!cbmvax!daveh      PLINK: D-DAVE H     BIX: hazy
		"I can't relax, 'cause I'm a Boinger!"