Voodoo5 5500 AGP and Asus P3B-F very odd behavior \ VOGONS

Voodoo5 5500 AGP and Asus P3B-F very odd behavior

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First post, by ux-3

Posted on 2010-05-12, 23:40

ux-3 Online

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Joined: 2004-05-12, 18:39

I'll give it to you without the long story:

My V5 5500 AGP won't work twin GPU on either 66 MHz fsb or 100fsb. But when I increase the FSB just one step (75 or 105), it works on all settings!

And that holds true for the KT133A Kinetiz too. fsb100 crashes. fsb102 flies.

I need an explaination! Please!

Reply 1 of 2, by h-a-l-9000

Posted on 2010-05-13, 00:27

h-a-l-9000 Offline

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Joined: 2005-02-23, 00:14

Is the 'spread spectrum modulated' setting enabled (if any)?

Also, at these frequencies the way the tracks are laid out on the PCBs do matter - reflections and signal delay depend on geometry and frequency. A different frequency causes different electrical properties. If it happens to be designed 'at the edge' incompatibilities may occur.

Otherwise, it could 'just' be some BIOS incompatibility. Or something completely different...

1+1=10

Reply 2 of 2, by ux-3

Posted on 2010-05-13, 09:43

ux-3 Online

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Joined: 2004-05-12, 18:39

You are right in a way - this morning I hit upon spread spectrum too. Now it works in my BX boards and the Via Board with spread spectrum disabled. The Kt133a gave me the clue, since it offers variable spreads. So it is an incompatibility of the card, not the boards.

Now I need to disable spread spectrum on the Asus P3B-F default settings.

Since the card always works on one chip, I suspect the synchronization of two GPUs with constantly changing AGP clock as the cause.

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