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From: daveh@cbmvax.UUCP (Dave Haynie)
Newsgroups: comp.sys.amiga
Subject: Re: I can't write to my hard disk!!
Message-ID: <8085@cbmvax.UUCP>
Date: 4 Oct 89 16:53:56 GMT
References: <46373@bbn.COM>
Organization: Commodore Technology, West Chester, PA
Lines: 23

in article <46373@bbn.COM>, denbeste@bbn.com (Steven Den Beste) says:

> [Oh, by the way, after all of that, the 68020 running at 7.16MHZ doesn't give
> really impressive performance gains. Oddly, it does slow down the little tune
> during boot by probably a factor of 4 - which makes no sense to me. On the
> other hand, it speeds up the intro to Scrabble by probably a factor of 3 (cache
> effects on busy-wait loops?).]

That's not surprising -- if you turn the cache off, you'll go slower almost
all the time than the 68000.  The deal is that the 68020 really wants a 32
bit bus.  It always prefetches 32 bits for it's instruction pipleline, even
if only 16 will be needed.  So you end up throwing out words with the '020
that you'd never have fetched with the 68000.  The enabled cache generally
overcomes this slowdown, plus maybe 10% or so, so on the average, the '020
in its normal setup will go a tad faster than the 68000.  The only real
reason to buy a Midget Racer, or any 68020/68030 board without 32 bit wide
memory is for the floating point unit.

> Steven C. Den Beste        ||  denbeste@bbn.com (ARPA/CSNET)
-- 
Dave Haynie Commodore-Amiga (Systems Engineering) "The Crew That Never Rests"
   {uunet|pyramid|rutgers}!cbmvax!daveh      PLINK: hazy     BIX: hazy
                    Too much of everything is just enough