Path: utzoo!utgpu!cunews!bnrgate!bwdls61!bwdls58!mlord
From: mlord@bwdls58.bnr.ca (Mark Lord)
Newsgroups: comp.sys.ibm.pc.hardware
Subject: Re: Why I lower my CPU speed to 17.5MHz
Message-ID: <5540@bwdls58.UUCP>
Date: 6 Feb 91 03:26:06 GMT
References: <1991Feb5.172330.27155@d.cs.okstate.edu>
Sender: mlord@bwdls58.UUCP
Reply-To: mlord@bwdls58.bnr.ca (Mark Lord)
Organization: Bell-Northern Research, Ottawa, Canada
Lines: 35

In article <1991Feb5.172330.27155@d.cs.okstate.edu> ong@d.cs.okstate.edu (ONG ENG TENG) writes:
<
<After upping my 386SX from 16MHz to 20MHz (without heatsink or fan), it
<worked fine, and still will if I choose to run it at that speed.  But 
<after many hours of continuous operation, my fixed-HD (I have a
<fixed-HD and a SyQuest removable where I run off most of
<my softwares, the fixed-HD contains most "standard" programs like
<system programs, word processors, graphics editor, terminal emulator,
<etc, only) my fixed-HD started giving disk-read error.  To get rid of
<it, I simply do warm-boot (NO turning off the power). 
 ... guesses about cause deleted ...


This problem is most likely due to the higher expansion bus speed
due to the higher frequency clock oscillator (crystal).  A 16-Mhz SX
typically runs the bus at 1/2 cpu speed, giving a convenient 8Mhz bus
to match the AT spec.  

When one speeds up the CPU by changing the crystal, as ONG has done, 
the expansion bus will also be run faster in most cases.  Since it is
run at 1/2 CPU speed, this means 10Mhz instead of the standard 8Mhz.

Not all expansion cards can cope with faster bus rates.  In particular,
I once had a Western Digital disk controller that did not work reliably
in my 10Mhz AT clone, which ran the bus at 10Mhz.  In the non-turbo mode,
everything worked fine.

I suspect something similar is the culprit in this case.  In my own souped-up
system, everything is lucky enought to work fine on a 10Mhz bus (I have a 
souped up 16Mhz -> 20Mhz 386SX).
-- 
 ___Mark S. Lord__________________________________________
| ..uunet!bnrgate!mlord%bmerh724 | Climb Free Or Die (NH) |
| MLORD@BNR.CA   Ottawa, Ontario | Personal views only.   |
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