Member Avatar for Jupiter 2

What does it do?
On my P4P800 it goes as high as 256mb.
Does it affect my ram 1024mb.
My video card is 128mb
If I set it to 256mb, what will happen?
And anything at all that you know, please ...

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Dani AI

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gave a solid technical explanation of the AGP aperture and GART; the following points add practical context for a P4P800 + 1GB RAM + 128MB video card setup and cover things the original posts did not.

The Graphics Aperture option is an AGP-era/IGP BIOS setting and is effectively irrelevant for modern PCI Express cards. On systems with integrated Intel graphics the similarly named IGD/IGP Aperture behaves a bit differently (it controls BAR/window access for the IGP). See Intel’s description for IGD aperture behavior. (Intel documentation: https://www.intel.com/content/www/us/en/support/articles/000028294/graphics.html)

How to experiment safely (repeatable workflow):

  1. Record the current BIOS value.
  2. Run a repeatable, GPU-heavy test or benchmark and record results.
  3. Change the aperture value, reboot, run the same test and compare.
  4. If the machine fails to boot, restore defaults by clearing CMOS (jumper or remove battery) and restore the recorded value.

Two cautions to watch for:

  • On 32-bit systems a large aperture can contribute to the PCI “memory hole” and reduce the OS-visible RAM ceiling; this is a system address-space interaction rather than a sudden loss of physical RAM. (Background: PCI hole explanation: https://en.wikipedia.org/wiki/PCI_hole)
  • A larger aperture increases the GART bookkeeping (one entry per small page), which can increase driver/scan overhead in edge cases; large values are rarely a direct performance win. (AGP/GART details: https://www.techpowerup.com/articles/43)

If the system runs Linux, check boot logs for AGP/agpgart messages (for example, dmesg | grep -i agp) and inspect whether the kernel/driver accepted the aperture; vendor drivers and the kernel’s agpgart handling can affect whether changes actually take effect. (Linux AGP notes: https://download.nvidia.com/XFree86/Linux-x86_64/1.0-9639/README/appendix-f.html)

For the P4P800 + 128MB card case: a moderate aperture or the board default is normally fine; increasing to 256MB should not break anything but is unlikely to produce a measurable win unless a specific application shows texture swapping or stuttering during the tests described above.

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Member Avatar for seeyouentee

Hello mate this should help you

Graphics 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.
Enjoy.

commented: Thorough and informative +1
Member Avatar for Jupiter 2

Thorough and informative.

Thank you very much

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