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Simple mod to force an AGP 8x/4x display card to run at 4x?

by abf111 / January 10, 2010 1:33 PM PST

That's right, I'm trying to get my EVGA Geforce 6200 LE display card to run at it's LOWER speed. Unfortunately, my GA-7VAX motherboard's bios doesn't have a manual setting to do it (mobo & card are smart enough to select the higher 8x speed automatically). I've tried all the utilities (Powerstrip, RivaTune, etc.) suggested in various forums but none of them could change the 8x/4x setting either. Then it occurred to me, there might be an easy mod, like taping over a couple of pins on the card before inserting it into the AGP slot, that would fool the mobo/bios into thinking that the card only supported 4x and also fool the card into thinking that the mobo only supported 4x! Does anyone know if this can be done?

Now why, you might ask, do I want to do this? Well, I'm having some system stability problems when running 3D graphics. An upgraded PSU made no difference. Running at 4x would reduce the max load on several system components, which might help, and it's an easy mod to do and test, assuming it could be done.

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I thought it was 4X
by R. Proffitt Forum moderator / January 10, 2010 10:54 PM PST
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Maybe different revs
by abf111 / January 11, 2010 12:16 AM PST
In reply to: I thought it was 4X

Thanks Bob,

There does seem to be some confusion about what the GA-7VAX supports but Gigabyte's own website says "1 x AGP slot (8X/4X, AGP 3.0 compliant) , Supports 1.5v display card only":


which is slightly different from the manual I got with the board which says "1 AGP slot supports 8X/4X/2X mode (1.5V) & AGP 3.0 Compliant". In any case my bios setup reports it's set itself at 8X; Sandra & Powerstrip both report 8X/4X capable, and Sandra reports currently running in 8X mode. So I'd say the evidence strongly points to support for both 8x and 4x modes, and currently running at 8x rather than 4x.

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I remember this old discussion.
by R. Proffitt Forum moderator / January 11, 2010 12:24 AM PST
In reply to: Maybe different revs

This area is full of problems on how to tell the owner how it works when there is much to cover. For example no AGP slot has a set AGP voltage. That's set by the card. So many got confused over the 1.5V only line in the specs and no maker is going to write a tutorial on AGP so I'm going with it is already at 4x and will allow 8x cards since to block such would mean the end of the line for this board.

These old socket A boards are well known to be twitchy and for that we banned them from the shop repair shops. We'll only replace the motherboard and CPU combo since owners tended to want us to warrant the repairs. Since these were unstable back then and even more now this is why we had to do that policy change.

See if they offered a BIOS update and see if you can reduce the FSB clock rate which often reduces the AGP clock rate too.

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Things to consider, try.
by R. Proffitt Forum moderator / January 11, 2010 12:42 AM PST

Yes we all know the difference from 4x to 8x was minimal. Reference http://www.hardwarezone.com/articles/view.php?cid=3&id=562&pg=2

But to get this working I suggest looking for the most recent BIOS and hope they added it in.

Many of these old Socket A boards have BAD CAPS. See BAD CAPS on google and even if you don't have failed caps these boards even with a reduced clock rate need the caps replaced for a SIMPLE REASON. Ready? Electrolytic capacitors have only a few year lifespan. About 5 in consumer gear since they don't put big enough parts or quality parts in.

These socket A boards are best gifted to others so you don't lose your time chasing the ghosts out of them.

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"recent" is a relative term for this mobo
by abf111 / January 11, 2010 7:29 AM PST

I've had this system since 2003. Several disk, ram, PSU, CD, DVD upgrades along the way. Bios last updated in 2005 (to a 2004 bios). I remember one of the "new" bios features was added support for AGP 8x, but after the upgrade, the ability to select an AGP rate (previously between 2x and 4x) was no longer there. I upgraded the processor from a Duron CPU to a Sempron 3 years ago and to the Geforce 6200 card two years ago, and the system was still rock solid, though pretty sluggish on some 3D games. As a last hurrah, I upgraded to an overclocked Barton last month. Definitely got some pep back and still amazingly stable except for, most noticeably, certain 3D games.

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by R. Proffitt Forum moderator / January 11, 2010 7:54 AM PST

Somewhere about 52 to 88 there are notes about a tweak tool. Try that.

At 2003 the machine is well beyond any that the shop will accept for reasons given. The main reason is that even when the owner is told there is no warranty on the rescue we were still getting dragged into small claims court at times over lost data when the machine crashed later. Some just don't get it.

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I seem to have found it.
by R. Proffitt Forum moderator / January 11, 2010 1:10 AM PST
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Really for overclocking, not underclocking
by abf111 / January 11, 2010 8:03 AM PST

Thanks again Bob, but the CPU Host Clock Control is only able to bump UP the FSB speed from what's selected by dip switches. In my case, the FSB is set to 166 by dipswitch which can be raised in the bios by CPU HCC. Unfortunately, the PCI and AGP divisors aren't changed and the bios nicely shows how those busses would be overclocked along with the FSB. So to get lower than 166, I would have to set the FSB to 133 by dispswitch, and raise it up to near 166 in the bios, overclocking the PCI/AGP busses by 25%, which I'm sure wouldn't work.

By the way, I also managed to take a look at the AGP 3.0 spec. and this whole 4X/8X business is A LOT more complicated than I imagined! There are several permutations of semi-compatibility between AGP cards and AGP slots, and, for example, even for my card/slot (as near as I can determine) there is something called "8X signaling" that's automatically set by the hardware, that's different from the 8X/4X transfer mode which is set up through a whole other set of low level initializations, and the actual "4X" protocol may be different depending on the particular card/slot combination! So I withdraw my original query.

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Try that.
by R. Proffitt Forum moderator / January 11, 2010 11:02 AM PST

set the FSB to 133 by dispswitch

And leave it there. For years I would pull back the FSB so owners could run their machines. The question was not that it ran slowly but that it would crash too often when at full speed. So they would settle for "running slower" rather than "crashing fast."

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