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List:       linux-smp
Subject:    Re: tweaking the Tyan Tomcat III bus speed...?
From:       "Dave Cinege" <dcinege () psychosis ! com>
Date:       1997-10-30 15:05:47
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On Thu, 30 Oct 1997 08:33:36 -0600 (CST), Brynn Rogers wrote:

>
>
>On Wed, 29 Oct 1997 hixson@frozenwave.com wrote:
>
>> On 29 Oct, Dave Cinege wrote:
>> > On Wed, 29 Oct 1997 13:42:02 +0000 (GMT), hixson@frozenwave.com 
wrote:
>> > 
>> >>Hi,
>> >> I was just wondering if anyone has been able to tweak their Tomcat III
>> >>so that the bus runs at either 75 or 83 Mhz.   I have two P133's.
>> > 
>> > The clock generator used on that board does not go above 66MHz when using 
a 
>> > 14.318MHz reference. The only way to go faster is to get out the soldering 
iron....
>> 
>> I have one, can you send me some instructions... :)
>>   -M@
>
>I think the easiest thing to do would be to change that reference crystal.
>Take a crystal that is 14.318*66/50 Mhz, then if you set the bus speed to
>50Mhz, it should really be 66Mhz,   setting to 60Mhz would be 73Mhz, and setting
>to 66Mhz will give 87.23.  or pick a different frequency to get whatever speed
>you want.  I have heard that the Real Time clock will be hosed by such a
>procedure.

This will hose your 24MHz reference for the onboard I/O chip. You must lift a pin 
on the clock gen, and hack the output of the real 24MHz osc onto the to get it 
working again.

This is what I have done and it has been running for about 9 months now.

Dual 150MHz PPro's OCed to 180MHz @ 90MHz x 2. Tyan S1668D....same 
ICS clock generator as the Tomcat III.

A BIOS anomoly screws the time up, since jumper setting refernece a differnet 
speed (IE I am at 180MHz but my jumpers corispond to 120MHz, time is scewed 
porpotionately) The RTC works fine and thus under OS/2 the time is fine, but linux 
does not use the RTC by defaut.


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