WTF is AGP Comp. Driving???

[Black_Cat]

Can anyone explain AGP Comp. Driving? I have had a few boards with this feature. The only settings that ever seem to work are DA and EA. What do these numbers represent and why are they in hex?

To start press any key. Where's the "any" key? --Homer Simpson.

 

[phsstpok]

I can give you a little more information but not a complete answer. Yes, the numbers you see are in hex. In some BIOSes you will see them listed as P-Control and N-Control but they are discreet values (0 thru F). In other BIOSes you'll see them as a double digit number but it still control the P value and the N value.

What are the P value and the N value? I don't know. Some people have said the are voltage modifiers for the AGP signaling. Other people say they relate to AGP timing.

How are these values are used? This is just as, or even more confusing. I have seen recommendations to change these values to fix anything from stability issues, to incomplete rendering and partial wireframes, to resolve boot problems, to resolving corrupt textures. Mostly these were claims with the old Geforce256 card which mostly had problems because older motherboards couldn't handle the high amount of current the card needed.

There is one thing I know for certain about the AGP Comp Driving or AGP Driving Strength. Increase the values if you think it will help but <b>never lower the value below default</b>. Remember they are two discreet values. If the default is DA then don't lower the first value below D and don't lower the second value below A. Lowering the values can disable video even during POST. Clearing CMOS does not recover things. The only fix is to use a PCI video card and change the settings back.

<b>I type sixty words per minute. Ten are spelled correctly.</b>

 

[Black_Cat]

I have seen recommendations to change these values to fix anything from stability issues

I can't imagine trying all those settings (00 to FF) to acheive stability. That would take all day! Thanks for the info.

On this POS MSI 694TPRO that I'm using the default was actually CB which would crash in 3D apps. Why on Earth would that be the default? I had to jar the old noggin to remember which were the two stable settings.

To start press any key. Where's the "any" key? --Homer Simpson.

 

[phsstpok]

I can't imagine trying all those settings (00 to FF) to acheive stability. That would take all day! Thanks for the info.

On this POS MSI 694TPRO that I'm using the default was actually CB which would crash in 3D apps. Why on Earth would that be the default? I had to jar the old noggin to remember which were the two stable settings.

Unlike most motherboards settings, AGP driving strength is one that should not be experimented with agressively. Most of what I learned about it I learned at the Geforce FAQ (my link is now dead so they must have moved again). It was mostly for Geforce256 and TNT2 cards, anyway. According to that site there were some specific recommendations for a few video cards from specific manufacturers. For those old nVidia cards the recommendation was to try "EA" or "FF". Other than that it was trial and error with the risk of crippling your motherboard. A utility, WPCREDIT, was useful for older VIA chipsets. You could tweak AGP driving Strenth after Windows has loaded. If you got careless with your settings with WPCredit no harm done, unlike using the BIOS settings to do it.

<b>I type sixty words per minute. Ten are spelled correctly.</b>