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Guest DanWalloch

AGP texturing - How does it work?

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I dunno if anyone can answer this question, but it's been bugging me for a while...I had a pretty old slow system, and as many other people discovered that if I drop the AGP texturing down to 16MB in the BIOS I get much better performance (ie with AGP texturing high I get short pauses whenever new textures are loaded in)...I just bought a powerhouse and AGP is at 64 MB by default (as on most new mobos), and same thing again, I'll have to change it in the BIOS to get rid of pauses. BTW, this is not only FS2002, this is practically all my games...Bottomline, keep AGP texture size small... (I came to that conclusion 2 years ago, and it has been reconfirmed even with a modern system)...Now, being naturally curious, I wonder why this is. I always thought that the main purpose of AGP is to speed up the texture transfer between system and graphics RAM. PCI was too slow, hence AGP... The odd thing seems that with limiting the AGP memory, you get pauses. Doesn't seem to make sense to me.On a side note, I read about a year ago on Tom's HWG that since Win ME, the OS is managing the AGP texture size and will override the BIOS setting. That's not true from what I've experienced...Does anyone here know the full story? Cheers, Christian

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I can only guess based on the few facts I know....The general purpose of AGP is to allow a card with say, 32 megs of graphics RAM access to additional mainboard RAM for texture loads. The alternative is where I'm a bit fuzzy, but I believe without AGP, when graphics RAM is exceeded textures are somehow "paged" in piecemeal, making for a slow redraw.Much depends on the sim or game and how much graphics RAM it uses. I believe now that many of our graphics card are 64 megs and beyond, it is fairly rare for AGP features to be required, although I'm sure new titles will challenge that.I think what we may be seeing when we "turn off" AGP by dropping the texture size is the turning off of the overhead required for DirectX to check whether mainboard RAM is needed. IOTW, we're saying "to heck with it", page piecemeal vs. AGP. And our newer cards have sufficient graphics RAM that the piecemeal paging isn't required.As I said, this is a guess. Most of my system support chores involve replacing or upgrading graphics cards, but the tech detail behind how they work is probably better explained by someone more up on the technology. -John

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By disabling AGP Texturing in Direct X, I was able to pick up another 5-10 fps and still having the same excellent graphics, plus a little more! :-)

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