This is a real tech question guys I need to understand.

Hi.

I have an AGP Radeon 9550 with 256 megs of video memory.

I have 512 megs of system, and Intel celeron 2.6 ghz, running windows XP (sp1).

Max size in BIOS is 256. (Bios fully up todate).

What size should I really have my apeture setting that would improve preformance not only for Civ 4, and would not impact others games I have such as Call of Duty 2, Brothers in arms, and BIA2 (EIB)?

I have some knoweldge of BIOS settings in general, but not enough to actually get a setting that would improve the overall preformance for all games out there.

One more thing. Why would I require more video memory when I have 256 megs onboard anyway? Wouldn't it be better to lower the apeture size to 32, or even 16?

Chat later...

Setting the BIOS setting too high can actually be counter productive. The higher the aperture, the more main system RAM is needed to table the graphics for the card. I have mine set 128mb and it seems happy enough throughout all the applications with 1Gb of RAM. Could always try dropping the AGP speed down to 4x since no card actually uses the full bandwidth of the AGP port and it never will since the new standard of PCI-e systems are now available.

Zanmato said:

Setting the BIOS setting too high can actually be counter productive. The higher the aperture, the more main system RAM is needed to table the graphics for the card. I have mine set 128mb and it seems happy enough throughout all the applications with 1Gb of RAM. Could always try dropping the AGP speed down to 4x since no card actually uses the full bandwidth of the AGP port and it never will since the new standard of PCI-e systems are now available.

Click to expand...

Hi.

Thanks, I appreciate the help. I'll try your suggestion.

Later!

Mikesla said:

One more thing. Why would I require more video memory when I have 256 megs onboard anyway? Wouldn't it be better to lower the apeture size to 32, or even 16?

Click to expand...

Short answer: It doesn't matter.

Long answer:
I doubt CivIV would attempt to allocate more than 256MB from the card and force part of textures to use the GART address space. System RAM will only be used when the frame buffer takes too much of the onboard video RAM and that would leave too little space for textures. That large frame buffer would require insane resolution with huge matrixes for Z transformations (=lots of AA&AF) and at the same time disabling Z buffer compressions. There are formulas to calculate how much memory is required, giving out an estimate when compression is considered, but I don't think that's a factor with anything below 1600x1200 with high number of samples.

But, in any case, no system RAM will be actually reserved when there are no calls from the app to take it! The BIOS "AGP Aperture Size" is a LIMIT on how much at maximum is allowed to be allocated, because this is the size of the virtual memory space, only filled from physical system RAM when required.

I haven't really looked at it, but CivIV shouldn't try to use it in normal operation. In that case, with 256MB cards at typical resolutions it shouldn't matter at all what you set the AGP Aperture size at, it won't be used. With 128MB and less cards I would set it so that at least 256MB is available total, if I had at least 1GB of system RAM. In the end, it's still only a minor performance issue if the game is properly coded, because if you need to use the system ram for textures, it doesn't matter much what layer manages them (OS GART drivers, Direct3D, your own code), it's still mostly limited by the latency between your GPU and where the memory is physically located. Differences between various modes of managing them are differences in CPU cycles spent. They won't matter much, unless you have a very slow CPU and very high performance graphics. Even then, we should be talking about a few to ten percent, nothing spectacular.

One way to look at the AGP Aperture scheme is that it's just using of system RAM for graphics with a MB chipset driven system which doesn't load the CPU to pass those bits. Basically DMA over AGP. You shouldn't worry about it that much, because it's finetuning, not something which will save or doom you if you have performance issues to begin with.