BIOS Settings and AGP Aperture Size - How to set them correctly
 

Apart from the fact that a lot of people are confused about the AGP aperture size setting, the BIOS guide linked to below is an excellent guide if you not sure about certain settings in your BIOS and what they do, i found it to be a very helpful aid and hopefully you will get some use out of it too.

I specifed the AGP Aperture size specifically as this seems to be one of the main settings that cause confusion, for example i have seen degredation in performance if i have it se to 256Meg, which i thought would be the right setting for my X800 with 256 onboard, insted i have it now set at 64 and have seen less stuttering in games.

From Rojacks BIOS Guide

AGP Aperture Size

Common Options : 4, 8, 16, 32, 64, 128, 256

Quick Review

This BIOS feature does two things. It selects the size of the AGP aperture and it determines the size of the GART (Graphics Address Relocation Table).

The aperture is a portion of the PCI memory address range that is dedicated for use as AGP memory address space while the GART is a translation table that translates AGP memory addresses into actual memory addresses which are often fragmented. The GART allows the graphics card to see the memory region available to it as a contiguous piece of memory range.

Host cycles that hit the aperture range are forwarded to the AGP bus without need for translation. The aperture size also determines the maximum amount of system memory that can be allocated to the AGP graphics card for texture storage.

Please note that the AGP aperture is merely address space, not actual physical memory in use. Although it is very common to hear people recommending that the AGP aperture size should be half the size of system memory, that is wrong!

The requirement for AGP memory space shrinks as the graphics card's local memory increases in size. This is because the graphics card will have more local memory to dedicate to texture storage. So, if you upgrade to a graphics card with more memory, you shouldn't be "deceived" into thinking that you will need even more AGP memory! On the contrary, a smaller AGP memory space will be required.

It is recommended that you keep the AGP aperture around 64MB to 128MB in size, even if your graphics card has a lot of onboard memory. This allows flexibility in the event that you actually need extra memory for texture storage. It will also keep the GART (Graphics Address Relocation Table) within a reasonable size.

Re: BIOS Settings and AGP Aperture Size - How to set them correctly
 

Here are the recommended settings for ATi cards ;)

btw AGP Aperture Size is the amount of system RAM your AGP card will use when it has run out of onboard video memory. The problem with higher settings is that the GART table becomes too large and unoptimised.

Re: BIOS Settings and AGP Aperture Size - How to set them correctly
 

Might just turn mine down to 64MB then.

Re: BIOS Settings and AGP Aperture Size - How to set them correctly
 

Mines been on 64 since I had enough memory to move up from 32, thats about 6 years. Before that I dont think I had an AGP slot, come to think of it I only had 32MB PC66 RAM in total.