AGP BIOS settings

[SweFred]

In the BIOS there are two settings which I would like to know what they mean:

Frame Buffer size
AGP aperture size (MB)

they are now both set to 32M. Could someone explain them and what should they be set to for optimal performance.

System specs:

Athlon XP 2400+
Epox 8RDA+
Sapphire Radeon 9700
WinXP Sp1


Cheers,

Fred

[refermadness]

8rda+ FAQ

Frame Buffer Size - For the 8RDA/8RDA+, disable this! If you have the 8RGA+, this setting specifies how much ram you want to dedicate to the onboard video. The default is 32mb, but I would recommend using 64mb if you have 265mb or more.

AGP Aperture Size (MB) - This setting basically extends your video memory into system memory. I don't really have an explanation why this is necessary, especially now that most never video cards have 128mb of onboard memory, but it really does help performance in games and in benchmark programs like 3dmark. If you have 256mb of ram or less, set this to 64mb. If you have more then 256mb of ram, set this to 128mb.

[Aedan]

The AGP Aperture size sets two things.

Firstly it sets aside an area of system RAM for use by the AGP card. This RAM is used for texture storage by the AGP card.

Secondly, it sets the size of the address "window" that the processor can talk to the AGP card's RAM through. This window is part of the PCI address space, so that the processor does not have to do any translation to talk to the AGP card's RAM. This is also an uncached area of memory, as both the CPU and AGP card can make modifications. Oddly enough, that's what the Microsoft AMD patch is for.

Increasing the size of the aperture will increase the size of the GART table, and hence the memory requirements. Of course, a lot of this space is actually "virtual" memory, rather than physical memory. Physical memory gets pulled into the pool as and when required.

As the system needs 12Mb to keep the virtual addressing tables, the AGP Aperture should be larger than that!

Áedán