Path: utzoo!utgpu!news-server.csri.toronto.edu!mailrus!bbn.com!sher
From: sher@bbn.com (Lawrence D. Sher)
Newsgroups: comp.sys.ibm.pc
Subject: Re: Can you speed up an old 6Mhz IBM-AT to 12Mhz?
Message-ID: <57993@bbn.BBN.COM>
Date: 5 Jul 90 19:05:22 GMT
References: <6692@vax1.acs.udel.EDU>
Sender: news@bbn.com
Reply-To: sher@labs-n.bbn.com (Lawrence D. Sher)
Organization: Bolt Beranek and Newman Inc., Cambridge MA
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In article <6692@vax1.acs.udel.EDU> bach@vax1.udel.edu (Baskaran Subramaniam) writes:
>Is it possible to speed up an old 6Mhz IBM-AT (not a compatible) to 12Mhz
>by changing the crystal in it?
>
>We have an 80287/6Mhz and 512K RAM+1128K AST Rampage card in it. I think, the 
>RAM chips have a speed of 120ns.  Would changing the crystal create any problem
>with using these?  Do I have to change the '287 and the RAM chips also?  Do I
>have to change the '286 chip itself?

Putting in a higher speed crystal will work, with increasing flakiness the
higher the speed.  My experience is limited, but I believe it is very unlikely
that you will be successful at 12 MHz (24 MHz crystal).  The "ISA" bus has a
practical upper limit of just about 8 MHz.  Even at 8.5 MHz, you may already
find some intermittent trouble, like in the disk controller.  I wouldn't try
for more than 8.0 MHz.