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AGP Aperture Size MOBO setting

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IdL3 H@Nd$

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Joined
Nov 14, 2002
Location
Minnesota
Just curious, in my BIOS should I have my aperture size set to 128 for a Radeon 9700 or leave it to the default of 64? I thought that I read somewhere that it was multiplied X 2 but I thought I would ask.

Thanks.
 
This is from Adrian Rojak's Bios Guide


AGP Aperture Size (MB)
Options : 4, 8, 16, 32, 64, 128, 256
This option selects the size of the AGP aperture. The aperture is a portion of the PCI
memory address range dedicated as graphics memory address space. Host cycles
that hit the aperture range are forwarded to the AGP without need for translation.
This size also determines the maximum amount of system RAM that can be allocated
to the graphics card for texture storage.
AGP Aperture size is set by the formula : maximum usable AGP memory size x 2
plus 12MB. That means that usable AGP memory size is less than half of the AGP
aperture size. That's because the system needs AGP memory (uncached) plus an
equal amount of write combined memory area and an additional 12MB for virtual
addressing. This is address space, not physical memory used. The physical memory
is allocated and released as needed only when Direct3D makes a "create non-local
surface" call.
Win95 (with VGARTD.VXD) and Win98 use a "waterfall effect". Surfaces are created
first in local memory. When that memory is full, surface creation spills over into AGP
memory and then system memory. So, memory usage is automatically optimized for
each application. AGP and system memory are not used unless absolutely necessary.
The size of the aperture does not correspond to performance so increasing it to
gargantuan proportions will not improve performance. Many graphics card, however,
will require a larger than 8MB AGP aperture size to work properly so you will need to
set a minimum of 16MB for the AGP aperture size. Even then, you should set the
aperture size at a higher setting so that it will be large enough to accommodate any
texture storage requirements that your games/applications may have.
At the moment, the rule of the thumb is an AGP aperture size of about 64MB to
128MB. Increasing the AGP aperture size beyond 128MB wouldn't really hurt
performance but it would still be best to keep the aperture size to about 64MB-
128MB so that the GART table won't be too large. As the amount of onboard RAM
increases and texture compression becomes commonplace, there's less of a need for
the AGP aperture size to increase beyond 64MB. So, it's recommended that you set
the AGP Aperture Size as 64MB or at most, 128MB.
 
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