Path: utzoo!utgpu!watserv1!watmath!att!tut.cis.ohio-state.edu!cs.utexas.edu!uunet!cbmvax!daveh
From: daveh@cbmvax.commodore.com (Dave Haynie)
Newsgroups: comp.sys.amiga.hardware
Subject: Re: Can I Speed Up a 25Mhz 030 Board?
Message-ID: <14316@cbmvax.commodore.com>
Date: 10 Sep 90 17:35:34 GMT
References: <4278@crash.cts.com>
Reply-To: daveh@cbmvax.commodore.com (Dave Haynie)
Organization: Commodore, West Chester, PA
Lines: 32

In article <4278@crash.cts.com> danb20@pro-graphics.cts.com (Dan Bachmann) writes:
>In-Reply-To: message from schur@isi.edu

>                In the September 1990 of Amazing Amiga Computing magazine it
>explains that you can increase your 25MHz Commodore 68030 board by replacing
>the 4 pin 25Mhz Crystal with a 28-29MHz crystal no problem 

They're counting on a considerable amount of luck here.  Most designs, the
A2630 included, have a bit of design margin; they're at the least designed
to work at worst case, where the temperature is a hot as it gets and all chips
are as slow as they get.  So it stands to reason that, when you're not going
at worst case, you might go faster.  Not every IC is going to be at its 
slowest possible timing, and you're rarely running at the full 40C ambient
temperature.  Going to a faster clock speed will most likely produce a number
of machines that just plain fail at room temperature, the majority which will
probably fail when they get too warm, and a couple which will work 100% 
throughout the temperature range.  

It's not even quite as nice as that, though.  The 68030, for instance, is
only rated at 25MHz.  When you feed it a faster clock, it can start behaving
out of spec, which can further stress the speed of the system.  This clock
mod is a do-at-your-own-risk kind of thing, of course, but even still, I
wouldn't recommend it.

I may eventually come out with a safer A2630 speedup modification, since so
many folks keep asking about it.  But such a speedup, done correctly, will 
cost much more.

-- 
Dave Haynie Commodore-Amiga (Amiga 3000) "The Crew That Never Rests"
   {uunet|pyramid|rutgers}!cbmvax!daveh      PLINK: hazy     BIX: hazy
      Get that coffee outta my face, put a Margarita in its place!