Path: utzoo!utgpu!news-server.csri.toronto.edu!rpi!usc!wuarchive!zaphod.mps.ohio-state.edu!unix.cis.pitt.edu!dsinc!bagate!cbmvax!daveh
From: daveh@cbmvax.commodore.com (Dave Haynie)
Newsgroups: comp.sys.amiga.hardware
Subject: Re: A3000: 16MHz vs. 25MHz
Message-ID: <21601@cbmvax.commodore.com>
Date: 15 May 91 16:33:10 GMT
References: <1991May11.150058.4684@vax5.cit.cornell.edu> <4502@bnr-rsc.UUCP>
Reply-To: daveh@cbmvax.commodore.com (Dave Haynie)
Distribution: comp
Organization: Commodore, West Chester, PA
Lines: 23

In article <4502@bnr-rsc.UUCP> mascot@bnr.ca (Scott Mason) writes:
>In article <1991May11.150058.4684@vax5.cit.cornell.edu> kzyx@vax5.cit.cornell.edu writes:

>>	I wonder how much I have to change to get a 25 MHz 040 in a 16MHz
>>stock A3000.

>The 68040 implements a very different bus interface from the 68030.
>The amount of logic required to interface an 040 to a 68000 or
>68030 slave is nontrivial.

Well, that's a matter of what you consider trivial.  It's certainly not a "do
it yourself" exercise, unless you're an experienced hardware hacker.  It's also
not earthshakingly hard, either.  The bus conversion logic for 68030->68000,
68040->68000, or 68040->68030, is typically a couple of PALs and a handful of
buffer chips.  A designer can increase the performance of such a system by
adding more logic, but a basic converter isn't very difficult.  In fact, when
the 68040 stuff first came out, Motorola published an application note on how
to convert a 68040 bus to a 68030 bus.  I don't know if it's an optimal design,
but it does appear to work.
-- 
Dave Haynie Commodore-Amiga (Amiga 3000) "The Crew That Never Rests"
   {uunet|pyramid|rutgers}!cbmvax!daveh      PLINK: hazy     BIX: hazy
      "That's me in the corner, that's me in the spotlight" -R.E.M.