What is AGP Aperture Size?

[W1zzard]

How big should I set AGP Aperture size in my BIOS?

First of all, AGP Aperture memory will not be used until your video card's on-board memory is running low. That means it will usually not impact your gaming performance because developers are trying hard to not exceed the on-board memory limits.
The bigger your video memory, the smaller your Aperture Size could be. However with later games requiring more and more texture memory a good number seems to be 128MB Aperture Size for all cards with 64 MB to 256 MB Video RAM.
Setting the Aperture Size to HUGE values will not increase performance because this merely sets the maximum amount of physical memory that can be used. It only makes the GART Table bigger because every 4K page has its own entry, no matter if allocated or not.
Setting the Aperture Size to too small values could result in running out of available texture memory especially on a low-mem video card. It is also possible that developers make use of the GART's features by creating textures as 'non-local'.

If you experience in-game stuttering try playing with the size of your Aperture.

What is it from a technical point of view?

When using an AGP card the video memory on the graphics adapter is mapped into the 4 GB memory address space (above the region of the physical installed memory). Any accesses to this memory region are directly forwarded to the video memory, greatly increasing transfer rates. However in earlier days of video cards graphics memory was rather limited and ran out quickly (a single 32-bit 512x512 MIP-mapped texture consumes ~1.5 MB) so AGP added a mechanism to use the system's main memory as additional storage for graphics data such as textures. This is what the AGP Aperture is. Usually directly below the mapped video memory the system reserves a contiguous space of addresses the size of your Aperture (no physical memory will be consumed at this time).
When free video RAM is running low the system dynamically allocates 4K sized pages of system memory for use as AGP Aperture Memory. The problem with this dynamic allocation is that in many cases the pages are spread in a non-contiguous form throughout the physical memory. Accessing these pages directly would hinder performance because of scattering/gathering requiring extra logic. To get around this limitation the GART (Graphics Address Remapping Table) which is implemented in hardware in the Northbridge's Memory Controller Hub provides an automatic physical-to-physical mapping between the scattered pages and the AGP Aperture. See the following illustration:
http://www.techpowerup.com/articles/43/images/aperture.gif

The actual usable amount of this 'virtual' AGP memory is less than half the AGP Aperture size set in the BIOS. This is because the Aperture is divided into two areas. One uncached half and another write-combined area.

[sandy]

MY PC CONFIGURATION IS:

p4 1.8gzh intel 845gebv2 motherboard
256 mb ram 7200 rpm samgsung hdd
ATI 9600 128mb agp

when i set the agp aperture size more than 64 mb the games pauses after every five or six seconds and its pretty much unplayable. But when i set the aperture size to 16 mb the games are playable smoothly without any pauses. I am pretty much confused as you said that setting the bigger aperture size would not be any problem, so could you please help me out with my problem...is there anything wrong with my hardware?? Or is there anything else i am missing out.
i will be highly oblieged if you guide me out of this problem.

thank you in advance

[DanTheBanjoman]

When you have a high aperture size you allow graphics to use up your system memory which is slower than the video memory. It seems that less faster memory is prefered.
Or graphics could be using your system memory and leaving nothing for other things, seeing that you have only 256Mb.
At least this is how I understand it.

Either way if things work fine with 16Mb aperture I see no problem, keep it that way.

[cram]

Or graphics could be using your system memory and leaving nothing for other things
Yep, this sounds right. If you can afford it, getting more system RAM should help a lot.

[sandy]

[QUOTE=sandy]MY PC CONFIGURATION IS:

p4 1.8gzh intel 845gebv2 motherboard
256 mb ram 7200 rpm samgsung hdd
ATI 9600 128mb agp

when i set the agp aperture size more than 64 mb the games pauses after every five or six seconds and its pretty much unplayable. But when i set the aperture size to 16 mb the games are playable smoothly without any pauses. I am pretty much confused as you said that setting the bigger aperture size would not be any problem, so could you please help me out with my problem...is there anything wrong with my hardware?? Or is there anything else i am missing out.
i will be highly oblieged if you guide me out of this problem.

thank you in advance

i did some experiments with different aperture size...when i increase the size to 128 mb there is a performance increase in games like "far cry" ,"unreal 2" ...but in games like "need for speed underground" and "spider 2"the problem occurs that the game pauses after every 4 or 5 seconds.But in this case eg. nfs underground,when after finishing a level i again restart that same level instantly......voila there is not a single pause or glitch in the entire level and its pretty smoothly playable and, what do you know,the frame rates hav also increased...so again here it is pretty much confusing as i dont know what to do...i think i will have play every level twice. :( what should i do???

please help me any of you guys
thank you again

[warluck]

Put more memory and voila and more fun and good game .

[DualGraphicLowTech]

Low Tech ECS motherboard powered by SIS735 intergrated chipset.
Memory PC2100 768MB
80GB WD HD
AGP MX2-400 with 64 MB
PCI MX2-200 with 32 MB
Span XP onto two displays with 1024 x 768 at 32 bit and 75 hz.

Discussion on GAS setting.
At 32MB the system locked all the time and MS XP was telling me its a driver related issue! Hum?
At 64MB the system locked at boot and at inconvenient times. (Like just as I complete a complex graph in excel and attempt a save and print. Lost work! Agh!)
At 124MB the system ran much faster with no XP lock up smoother graphics.
At 256MB the system just pops the graphics from websites with smooth game play. (Note: This still leave me with 512 MB for the system)

By using 256MB GAS setting the system is using the cashe more effectively. I am able to open multiple applications and write papers with graphics. It has not cause any slow down or lockup. In fact as I increased the GAS the CPU usage went up slightly with smoother operations. The system have been in operation for 1-1/2 years. I started to play with the GAS setting after the last MS update. Turns out its not completely driver related. Nvidia released a great universal driver that allowed spanning dual displays and used a lot of memory. It was causing problems because the CPU was getting the computation completed and had no where to dump the information. Once I increased the gas the task manager show much higher usage of cashe and cpu. I am using more of my system resources effectively. The online videos are streaming faster and games are streaming faster.

The more I read about GAS, I have come to the following conclusion.

1) Systems these days require a minimum of 512MB to run CPU and apps smoothly.
2) Graphics require 256MB to run smoothly, this is the GAS setting.
3) Sum total of minimum memory is 768MB.
4) Never allow the GAS to exeed 1/2 of the total system memory, this is a formula to crash and lock XP. It does one heck of a number when it loops the memory and lock the system. Only a hard exit and system reboot will get you out.
5) DON'T RUN GRAPHIC CARD MEMORIES GREATER THAN SYSTEM MEMORY! Where the heck is the system going to get the data to dump onto the graphic cards?
6) Systems should have the same amount of memory as graphic card for GAS + double that memory to the system itself to run apps.

Dual graphic cards with 128MB = 256MB
GAS = 256MB
System = 512MB Min. more the better.

I would like to read some comments and response.

Please don't run 512MB GAS with 256MB on graphic board and 128MB system memory.

Dual Graphics Low Tech!

[POGE]

Sorry to dig up an old thread, but what is the PCI-E equivelent, if there is one?

[zekrahminator]

all I know is, that if you want to shut off AGP aperture COMPLETELY (and you have an ATI card on AGP bus), go into CCC "smartgart" and tell it to shut off AGP write.

[Lozza]

I find that when I set it to 512mb, it really helps in Battlefield 2 and Doom 3. I used to play Call Of Duty 2 with all textures on "High", and this was playable. After setting it to 512mb from 256mb, I can now play it with all the textures on "Extra". I'm quite happy.

[Atom_Anti]

I don`t understand this whole thing:confused:.
Somebody tell me, if I have a hd 3850 AGP with 512Mb memory, than which setting is the best to me!
Thanks in advance!

[Demos_sav]

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 that are often fragmented.The GART allows the graphics cards 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.

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, this is wrong!

The requirement for AGP memory space shrinks as the graphic's card's local memory increases in size. This is because the graphics card has 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 you need even more AGP memory! On the contrary, a smaller AGP memory space is 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 also keeps the GART within a reasonable size.

[Atom_Anti]

Thanks Dude!

[Demos_sav]

Thanks Dude!

No problem. Just remember....The more memory your graphics card has the less you should choose as aperture size. AND NOT VICE VERSA

[candle_86]

well if you didnt want to allocate any ram, couldnt you just not install the GART?

[Demos_sav]

well if you didnt want to allocate any ram, couldnt you just not install the GART?

Well you can't. It's installed by default and it is uninstallable. Only thing you can do is set its size

[Demos_sav]

Sorry to dig up an old thread, but what is the PCI-E equivelent, if there is one?

There is no equivelent in PCI-E. The only reason there is in AGP it's because of some older AGP cards having 32MB-64MB(or less). In the PCI-E, cards like that are very few so there is no reason for mobo manufacturers of creating GART and so adding more code in their already difficult to be coded bioses