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From: glen@intelca.UUCP
Newsgroups: net.micro,net.micro.pc
Subject: Re: Fast AT xtals?  How about fast XT xtals?
Message-ID: <201@intelca.UUCP>
Date: Wed, 29-Jan-86 17:30:13 EST
Article-I.D.: intelca.201
Posted: Wed Jan 29 17:30:13 1986
Date-Received: Sat, 1-Feb-86 07:40:54 EST
References: <11540@ucbvax.berkeley.edu.BERKELEY.EDU> <11541@ucbvax.berkeley.edu.BERKELEY.EDU>
Organization: Intel, Santa Clara, Ca.
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Xref: watmath net.micro:13663 net.micro.pc:6766

> 	I have replaced the 5Mhz 8088 with an 8Mhz V20, which works fine.
> But, when I replaced the clock chip with the one for the V20, I got a blank
> screen on cold-boot - not even a cursor.  The V20 type clock chip divides the
> xtal frequency by 1/2 instead of 1/3 and has a 50% duty instead of 33%.  All
> of this is fine for the V20, so something else must be going wrong.  If I had
> a 'scope, I could tell you more, but I don't.
> 
> 	Any clues to resolving this problem would be appreciated.
> 
> Thanks,
> Tim Iverson.
> (iverson@cory.berkeley.edu)

For a computer to run faster, not only must the CPU be able to run at a
higher clock rate, but so must the memory and I/O subsystems.

It just so happens that the memory and I/O of an AT can run at 8MHz (or in
some cases more).  I suspect the XT memory and/or I/O does not.

Also, if you have a Color/Graphics Adapter (as opposed to a IBM mono,
or Hercules, etc.) then the CPU XTAL also affects the display rate and
your monitor may not sync up.  (Even if it can, the CPU must run some
initialization code before you see the cursor).

-- 
^ ^    Glen Shires, Intel, Santa Clara, Ca.
O O     Usenet: {ucbvax!amd,pur-ee,hplabs}!intelca!glen
 >      ARPA:   "amd!intelca!glen"@BERKELEY
\-/    --- stay mellow