-= AGP memory from main memory =-

[SV]

Hi,

I have been googling for my 'problem' but not sure i found verified
information - so i'll try you guys.

If i have 1Gb of main-memory and in the BIOS set the AGP departure
size to be 256Mb - how would this show in any Windows version - will
it show the total physical memory as 1GB or will it just show 756Mb's.

On the site i found Windows Vista at least would show the 1GB and then
show how much memory the graphics card currently is using.

Thanks for any input on the topic.

/AGP-wondering Swede.

 

[jukka]

Hi,

Sup, bro?

If i have 1Gb of main-memory and in the BIOS set the AGP departure
size to be 256Mb - how would this show in any Windows version - will
it show the total physical memory as 1GB or will it just show 756Mb's.

It's AGP aperture. It doesn't consume any physical memory from your
system until these pages are actively used. It just means how many
entries there will be in the GART (Graphics Address Remapping Table),
each entry is 4 KB.

How this works, is that graphics card's memory is mapped into 32 bit
physical address. In this address range you will not have any
installed memory chips in the motherboard. Any write into these
addresses goes into the video card's memory instead.

Since the video cards have finite amount of memory, so-called AGP
aperture can be used to extend the amount of addressable memory.

Similar "trick" was used with VESA VBE 2 and later versions in the old
days.

On the site i found Windows Vista at least would show the 1GB and then
show how much memory the graphics card currently is using.

I could be wrong, but I think that's driver specific.. how it uses the
aperture. Example. You create and use more textures than fit into the
graphics card's memory, the driver will use the aperture (which means
slow-down) and starts claiming memory from the system.

 

[SV]

On Wed, 27 Jun 2007 14:01:31 -0700, "(e-mail address removed)"


Hi,

Thanks for taking the time - and above all - for correcting my
spelling mistake - this time i found a bit more - some agrees on what
you say but some didn't so i went to microsoft's site with the correct
spelllng where i found the information i needed.

Your input is valid for a 'Discrete Graphics Adapter' and i should
have mentioned i was referring to a laptop - thus it is an integrated
one.

http://download.microsoft.com/download/9/c/5/9c5b2167-8017-4bae-9fde-d599bac8184a/GraphicsMemory.doc

The example that starts on page 5 (swedish pageing) is exactly what i
had in my initial question.

Here it says the following about BIOS allocation for integrated
adapters.

BIOS allocation:

An integrated graphics adapter can reserve a dedicated portion of the
system memory during the System BIOS power-on self-test (POST) phase
of a system startup. This method effectively hides a portion of the
system memory from the operating system. Thus, the reserved memory is
not reported by the operating system as part of available memory
resources.

For example, if the BIOS reserves 256 MB of system memory from a
computer system with 1 GB of installed system memory, the operating
system can see and report only the remaining 768-MB memory to the user
through various control panels or through Windows APIs.

Thanks again for your input

Regards

/AGP-wiser Swede

 

[jukka]

Here it says the following about BIOS allocation for integrated
adapters.

BIOS allocation:

An integrated graphics adapter can reserve a dedicated portion of the
system memory during the System BIOS power-on self-test (POST) phase
of a system startup. This method effectively hides a portion of the
system memory from the operating system. Thus, the reserved memory is
not reported by the operating system as part of available memory
resources.

Ah, ofcourse, duh! My bad, didn't even think of that, they use so-
called UMA in the laptops heavily. UMA = Unified Memory Architecture,
short for crap. First UMA OGL machine I ever saw was SGI O2, those
sucked ballz pretty much. Heh.