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AGP Aperture Sizing in Bios

Posted: Sat Mar 10, 2007 8:03 pm
by fastturtle
I was checking the Sapphire forums and discovered an interesting tidbit about setting AGP aperture size for both the 96/98 series of cards. What they stated is that for maximum stability, use either a 64 or 128 meg aperture size with any of the cards, otherwise stability will suffer. :roll:

Of course this surprised the hell out of me because I've always set the aperture based upon how much memory the video card has as anything larger was wasted while going smaller would impact performance. Guess I didn't know what I was doing and will have to investigate it much further. :shock:

Another thing I discovered was that the 9600 series chips dislike having Fast Writes enabled and disable the video bios shadow feature as it's supposed to cause major issues with 9600 series cards. This is one thing I've always done so it's never affected me but according to the Sapphire forum sticky, it can cause boot failures with the 9600 series GPU's.

Posted: Sat Mar 10, 2007 9:22 pm
by TedMC
Check the "memory access" size of your card. I assume that the 9600 had 64 bit memory acess ...I think your aperture size should match that. My X800pro has 256 bit memory access so my aperture is set correspondingly to 256.
Check out the omega radeon drivers,there is a full description of the 9600/fast write situation.From my somewhat vague memory on the subject,fast writes was an old workaround to an old problem not apparent in modern video cards.
In other words it's not the "amount" of memory on the's the "memory bus width"

Posted: Sat Mar 10, 2007 10:49 pm
by Tephras

Posted: Sun Mar 11, 2007 6:19 am
by jhhoffma
I always keep mine set to 128MB. That usually is enough with newer AGP cards. Of course, I've had the experience with some games where I had to switch it to 256MB. But when I finished the game, I changed it back.

Anything to free up more system RAM...

Posted: Sun Mar 11, 2007 6:29 am
by fastturtle
TedMC: I'd never thought of it that way but it makes far more sense then configuring it to memory size.

Tephras: Interesting link on what AGP Aperture is but appears to be technically deficient based on how my motherboard docs have always explained it. Simply put the AGP Aperture is a specific section of memory that's immediately handed to the video card, it's not reserved as an amount, thus memory output that goes to the video card which hits the aperture size is sent straight to the card. Similar to DMA (direct memory access).

TedMC's explanation actually makes more sense in how to configure it as the actual GPU memory interface will set the aperture needs. In the case of my 9600Pro, this means I should be using an aperture of 128 for maximum throughput and stability because the cards specs have a 128 bit memory interface :)

Posted: Sun Mar 11, 2007 12:21 pm
by fastturtle
It's been an interesting learning experience with some very good explanations given by the Sapphire Forums. One thing I've always thought would improve performance on the 9600 was to enable fast writes for the AGP slot. Turns out the chip hates fast writes and it'll get very cranky. So leave em off.

Now all I can say is that once the RMA'd mobo gets back, I'll be doing some serious stability testing using the ATI tools. Definately want to crank the card to it's limits before depending on it. Consider this to be a burn in test and you'll be damn close to what I'm going to do to the poor thing. Of course there is another reason I'm going for this level of testing and that's because I'm considering an X16--Pro to run the Folding GPU client on if I can get the stability needed. Otherwise, I'll be getting a Geforce MX4000 and go back to CPU only folding. :cry:

Posted: Sun Mar 11, 2007 1:17 pm
by bonestonne
on my oldest board i have AGP Aperture set to 256, even though its running the 440GX chipset..for its age, its good. with over a gig of ram in that system, i see no real difference, but in theory, since it doesn't need graphic performance i could technically lower that and get better performance.

i guess my contribution is more along the lines of this:

Does having a higher Aperture size help your system any?