AGP Aperture size

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roger

Thanks for the answer to my previous question.
While in the Bios I noticed the AGP Aperture size. It is currently set to
64M.
What is it and should it be set to 256M for a 256MB card?

Regards
 
it determines how much sytem ram is reserved for agp textures i believe or
something or other generally from what i understand is you have it set to
half of your graphics ram so if you got a 256mb card set it to 128mb agp
aperture.
 
This discussion assumes a 128Mb card... and I'll probably get flamed by someone who totally
disagrees, but this is based on my experience of games, and the recomendations I have seen for
removing in-game glitches caused by people setting large apertures in the belief they are a good
thing...


Aperture is the maximum amount of mainboard memory that the GFX card will use as a buffer if it ever
runs out of its own memory. It is not actually set aside specifically for the GFX card, in that 'if
the card does not use it, neither does the OS'. What happens is that if the GFX card ever asks for
memory, the mobo says 'okay, here it is, you can have another xMb, because the aperture is yMb, and
if you ask for more than yMb, I will start streaming it into the aperture'.

For modern cards, you dont want the GFX card to try to use the aperture uless it absolutely has to,
because it may try to do so in-game, and this would cause a glitch (the transfer between the two
types of memory is slower than direct from GFX memory, and will continue to be so even for PC
Express). And anyway most cards have enough memory to not need to lload much data in game.

What you find with a high aperture is that in most games it makes no difference because they are
written to avoid the issue. the games load up the GFX card between levels or at points when the
game engine is paused (such as the pause between areas in Morrowind) simply avoid the issue. Also,
in level or 'room map' based games where they have a series of 'rooms' stitched together to give the
impression of a true world - basically every quake type shooter going - you will see little effect
in changing the aperture because it is just not used on a typical 128Mb card, because the data is
loaded 'per roon', and that occurs at the start of the level or at the a pause point in the game.

Where you *will* see a difference is games where there is no room based map, and you have a true
game world. Examples of this are typically advanced simulations - Operation flashpoint or Lock-on
come to mind. In such games, texture transfer occurs in-game, and the GFX card will be loading
textures from the aperture. Settng it high would seem to be a good idea, but experience with both
games shows that its actually better to keep it small - as low as 32M or 64M. If you set it high
(128M or 256M) you see massive stutters. Im not sure why, but the consensus seems to be that a low
aperture forces the card to not rely on the external memory, whereas setting it high makes it more
likely that the card requests loads of textures at a single instant, and this causes glitches.

There is a general rule that you should set the aperture at half the available memory, or at around
the same size as the GFX card memory, but I think that is just a load of crap, and is prolly totally
outdated manufacturors recomendations from a time when GFX cards only had 32Mb

Upshot - leave it where it is (64M) unless you see in game glitches. If you do see glitches, set
the aperture lower (increasing the AGP voltage is also noted in some places as fixing glitching, esp
when used with a low aperture). there may come a point later on when games start needing more than
128Mb, and if that happens you will have to increase the aperture, but by that time, the typical
128Mb card will be superceded IMO, and we will not be using them.

HTH

S
 
This is probably the most comprehensive explanation on AGP aperture size
I've seen in the last five years...

--
"War is the continuation of politics by other means.
It can therefore be said that politics is war without
bloodshed while war is politics with bloodshed."


Sham B said:
This discussion assumes a 128Mb card... and I'll probably get flamed by someone who totally
disagrees, but this is based on my experience of games, and the recomendations I have seen for
removing in-game glitches caused by people setting large apertures in the belief they are a good
thing...


Aperture is the maximum amount of mainboard memory that the GFX card will use as a buffer if it ever
runs out of its own memory. It is not actually set aside specifically for the GFX card, in that 'if
the card does not use it, neither does the OS'. What happens is that if the GFX card ever asks for
memory, the mobo says 'okay, here it is, you can have another xMb, because the aperture is yMb, and
if you ask for more than yMb, I will start streaming it into the aperture'.

For modern cards, you dont want the GFX card to try to use the aperture uless it absolutely has to,
because it may try to do so in-game, and this would cause a glitch (the transfer between the two
types of memory is slower than direct from GFX memory, and will continue to be so even for PC
Express). And anyway most cards have enough memory to not need to lload much data in game.

What you find with a high aperture is that in most games it makes no difference because they are
written to avoid the issue. the games load up the GFX card between levels or at points when the
game engine is paused (such as the pause between areas in Morrowind) simply avoid the issue. Also,
in level or 'room map' based games where they have a series of 'rooms' stitched together to give the
impression of a true world - basically every quake type shooter going - you will see little effect
in changing the aperture because it is just not used on a typical 128Mb card, because the data is
loaded 'per roon', and that occurs at the start of the level or at the a pause point in the game.

Where you *will* see a difference is games where there is no room based map, and you have a true
game world. Examples of this are typically advanced simulations -
Click to expand...
Operation flashpoint or Lock-on
come to mind. In such games, texture transfer occurs in-game, and the GFX card will be loading
textures from the aperture. Settng it high would seem to be a good idea, but experience with both
games shows that its actually better to keep it small - as low as 32M or 64M. If you set it high
(128M or 256M) you see massive stutters. Im not sure why, but the
Click to expand...
consensus seems to be that a low
aperture forces the card to not rely on the external memory, whereas setting it high makes it more
likely that the card requests loads of textures at a single instant, and this causes glitches.

There is a general rule that you should set the aperture at half the available memory, or at around
the same size as the GFX card memory, but I think that is just a load of crap, and is prolly totally
outdated manufacturors recomendations from a time when GFX cards only had 32Mb

Upshot - leave it where it is (64M) unless you see in game glitches. If you do see glitches, set
the aperture lower (increasing the AGP voltage is also noted in some
Click to expand...
places as fixing glitching, esp
 
roger said:
Thanks for the answer to my previous question.
While in the Bios I noticed the AGP Aperture size. It is currently set to
64M.
What is it and should it be set to 256M for a 256MB card?

Regards
Click to expand...

Sham B's explanation is good, overall.
If you set it too low (under 16 or maybe 32) you revert to 2x AGP, I
believe.
I read a few articles about testing the different Aperture setting
with various cards, and it didn't seem to make a lot of difference to
most cards. However, the commonly recommended settings was either 64
or 128MB.
Don't go below 32 and try up to the maximum you can set it to. You can
experiment yourself and let us know. You really can't mess anything up
trying, and , who knows, you might just find the 'sweet' spot for your
particular setup.
You can Google for more info on the sugject.
Adrian Rojak has something intersting words on it. Check his BIOS
stuff on his homepage:
http://www.rojakpot.com/
Click on the free version of
The Definitive BIOS Optimization Guide
Revision 8.0 Interim Release 9

Here is one of his statements about Aperture (he continues on with the
reasons, or at least his old version did):
"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!"


Buffalo
 
I think from what I have seen myself you will get about a 2% increase in
performance from 64mb to 128mb at least with newer model cards or it could
be mainly based on gf4 cards.
 
roger said:
Thanks for the answer to my previous question.
While in the Bios I noticed the AGP Aperture size. It is currently
set to 64M.
What is it and should it be set to 256M for a 256MB card?

Regards
Click to expand...

You don't want to be using the much slower system RAM to save textures.
Neither do games. From what I hear, games will try to limit the use of
system RAM (by not using it at all) and remain within the constraints of
the video RAM to remain fast. Just because you up the AGP aperture size
doesn't mean the game will use it as the game may restrict itself to
only using video RAM. Also, video resolution (usually selectable with a
game) can make an impact on whether or not system RAM will get used.
Note that just having a large AGP aperture specified does not used up
that memory until it actually gets asked for; however, the GART table
will get bigger.

There are problems with making the AGP aperture large under Windows 9x;
see http://support.microsoft.com/?id=253912. This does not apply under
Windows NT/2K/XP (but the GART is larger and thus uses more memory).
You never specified what operating system you are using (or if you are
even using Windows). The general rule is to make it half the size of
your system RAM (if half the size of system RAM is not a selection for
AGP aperture size in BIOS, then pick the next size under that).
However, you can also start a low AGP aperture size, play your game, and
check if it is jerky or slow, then up the AGP aperture size and check
again as you test at each setting to see if there really is any
improvement in game play.

Have a read at http://www.tweak3d.net/articles/aperture-size/ and
http://www.cybercpu.net/howto/basic/AGP_aperture/ (and part 2 at
http://www.cybercpu.net/howto/basic/AGP_aperture_2/index.asp). Although
these articles are dated back in 2002, the AGP 2.0 spec is dated back in
1998 (ftp://download.intel.com/technology/agp/downloads/agp20.pdf) and
AGP 3.0 is dated at 2002
(ftp://download.intel.com/technology/agp/downloads/agp30_final_10.pdf);
section 5.3 discusses AGP aperture. You'll have to check what AGP spec
your video card supports. What they do show is that the best AGP
aperture size depends on the application so each additional AGP aperture
increase may not afford an increase in the application (i.e., going
bigger can actually mean going slower). More user-informative articles
were found at http://www.ocfaq.com/article.php/overclocking/vidcard/43
and
http://www.adriansrojakpot.com/Speed_Demonz/New_BIOS_Guide/AGP_Aperture_Size.htm.
It comes down to: If you don't test it, you won't know. Plus setting it
optimal for one game or application won't necessarily make it optimal
for everything.
 
Thanks for the answer to my previous question.
While in the Bios I noticed the AGP Aperture size. It is currently set to
64M.
What is it and should it be set to 256M for a 256MB card?

Regards
Click to expand...
There is only one instance where I've seen AGP Aperture size
demonstratively come into play. If you've used the wrapper for the Ruby
demo, in the readme it says for 128 Mb cards you should set your AGP
Aperture to 256 Mb, this is absolutely true in order to get decent
performance out of that demo.
Otherwise I don't see any noticeable difference between 64 and 256.


--
"You keep using that word. I do not think it means what you think it means."

- Inigo Montoya
Steve [Inglo]
HES PORN
 
There is only one instance where I've seen AGP Aperture size
demonstratively come into play. If you've used the wrapper for the
Ruby demo, in the readme it says for 128 Mb cards you should set your
AGP Aperture to 256 Mb, this is absolutely true in order to get decent
performance out of that demo.
Otherwise I don't see any noticeable difference between 64 and 256.
Click to expand...
I should add that this somewhat leads me to believe that a 256 Mb
aperture may be advantageous for the next round of bleeding edge game
releases.
I guess we'll find out when Doom ]|[ and Half-Life 2 get here.
 
Inglo said:
There is only one instance where I've seen AGP Aperture size
demonstratively come into play. If you've used the wrapper for the
Ruby demo, in the readme it says for 128 Mb cards you should set your
AGP Aperture to 256 Mb, this is absolutely true in order to get decent
performance out of that demo.
Otherwise I don't see any noticeable difference between 64 and 256.
Click to expand...
I should add that this somewhat leads me to believe that a 256 Mb
aperture may be advantageous for the next round of bleeding edge game
releases.
I guess we'll find out when Doom ]|[ and Half-Life 2 get here.
Click to expand...

AGP Apreature is to the Video Memory like the Virtual (HDD) Memory is to
System Memory. When the Video memory becomes used up it uses the AGP
Apreture. It's only really noticable then the video games/program requires
more Video memory then is availiable on the card.

-Liggyman
 
Actually, I've tested some various settings, on older systems, if it
goes below 12k, directX shuts off and a reinstall wont bring it back.
 
The below sounds like a good plan. For 98SE I followed all the general rules
about setting AGP aperture size and certain maps in Battlefield 1942 and
BlooodRayne ran like slide shows at all resolutions. This was with a 9800 Pro
and a 9500 Pro under 98SE. When I increased my AGP aperture size to 512MB all
these problems disappeared. I know of at least one other person running 98SE
for which changing the AGP aperture size to 512MB cleared up problems for him.
Does anyone know why this works though?
even using Windows). The general rule is to make it half the size of
your system RAM (if half the size of system RAM is not a selection for
AGP aperture size in BIOS, then pick the next size under that).
However, you can also start a low AGP aperture size, play your game, and
check if it is jerky or slow, then up the AGP aperture size and check
again as you test at each setting to see if there really is any
improvement in game play.
Click to expand...


-Bill (remove "botizer" to reply via email)
 
roger said:
Thanks for the answer to my previous question.
While in the Bios I noticed the AGP Aperture size. It is currently set to
64M.
What is it and should it be set to 256M for a 256MB card?

Regards
Click to expand...

I seem to recall a test being done where they 16, 32, 64, 128 and 256. I
don't recall the card or game.

In that particular setup there was an inexplicable decrease in performance
at 32 (I think) with all other sizes being the same performance.

I think previous replies have demonstrated that there is no hard and fast
rule, everybody has a different opinion because everybody has seen differing
results because everybody has performed different tests.

In my opinion, Leave it at 64 or 128, it's not gonna make much odds.
However, depending on your card, game, chipset, your mileage WILL likely
vary. Feel free to test it out, but bear in mind that your results will be
specific to your chipset, memory, graphics card, game, phase of moon, colour
of underwear, etc.

Ben
 
Ben Pope wrote:

I seem to recall a test being done where they 16, 32, 64, 128 and
256. I don't recall the card or game.

In that particular setup there was an inexplicable decrease in
performance at 32 (I think) with all other sizes being the same
performance.

I think previous replies have demonstrated that there is no hard and
fast rule, everybody has a different opinion because everybody has
seen differing results because everybody has performed different
tests.

In my opinion, Leave it at 64 or 128, it's not gonna make much odds.
However, depending on your card, game, chipset, your mileage WILL
likely vary. Feel free to test it out, but bear in mind that your
results will be specific to your chipset, memory, graphics card,
game, phase of moon, colour of underwear, etc.
Click to expand...


http://tinyurl.com/5dntq

and

http://tinyurl.com/2fwol

regards
@ndrew
 
Buffalo said:
Sham B's explanation is good, overall.
If you set it too low (under 16 or maybe 32) you revert to 2x AGP, I
believe.
I read a few articles about testing the different Aperture setting
with various cards, and it didn't seem to make a lot of difference to
most cards. However, the commonly recommended settings was either 64
or 128MB.
Don't go below 32 and try up to the maximum you can set it to. You can
experiment yourself and let us know. You really can't mess anything up
trying, and , who knows, you might just find the 'sweet' spot for your
particular setup.
You can Google for more info on the sugject.
Adrian Rojak has something intersting words on it. Check his BIOS
stuff on his homepage:
http://www.rojakpot.com/
Click on the free version of
The Definitive BIOS Optimization Guide
Revision 8.0 Interim Release 9

Here is one of his statements about Aperture (he continues on with the
reasons, or at least his old version did):
"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!"


Buffalo
Click to expand...

I've found it also depends on the motherboard itself. On my current one
(GA 8IPE1000G) it doesn't seem to make a difference at all, unless set
to 0, then it won't start :) On some older ABit 440BX mobos, I have to
set it to 128 or 256 for it to start with a 128 meg card in the AGP
slot. The BE6-II is one I still use that this happens with. Other than
this, I've seen no difference whatever in game no matter what I have the
AGP aperture set to. system ram in the BE6-II is 768 megs under 98SE,
System ram in the 8IPE1000G is 1 gig under XP Pro.
McG.
 
I don't know what mobo you're using, but on the 7 ABit (440BX), and 5
Gigabyte (for P4's) I have yet to see an aperture setting available
greater than 256 megs. I didn't even know some had 512megs available!
McG.
 
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