1024 high vs 640 low

[Marsumane]

Heres the deal:
I just built a computer for someone who purchased a 2500+ sempron processor (@ 2ghz right now), 512mb pc3200 ram and a 5700le (@420/620 compared to 225/400) which has a 64 bit memory bus which leaves it around ~5gbps for memory bandwidth.

Now this card is obviously bottlenecked on the memory bus. So i turned down doom 3 and im getting around 31fps by using the demo1 test at 640 low settings, everything off (shadows, bumpmapping, etc). Then i ran it at 1024 high settings with all other options off (shadows, bumpmapping, etc) and i got EXACTLY (to the tenth of a frame) framerate! Id figure that this game is bottlenecked by the 64bit memory bus and id figure that turning up the res and settings would take up more of that bus. These settings seem to take up NONE of the memory bus what-so-ever as compared to the lowest setting.

I can fathom the higher res not taking up more due to it being mostly fillrate limited, but the fact that less compressed mapping of all sorts takes up NO memory bandwidth leaved me puzzled. I know carmack is a good coder, but I didnt think he was this good. Basically my question is what exactly (besides vram) does the higher doom settings take up? And why doesnt less compressed textures, maps, etc take up more room on the bus?

 

[Slaimus]

Did you timedemo multiple times? The first time you do it, it is usually disk limited as it is dynamically loading a lot of the data.

 

[BFG10K]

Turn off vsync & AA and try again. Also make sure AGP is working properly (use the latest chipset drivers if it isn't).

If it still runs the same you are CPU limited.

 

[Marsumane]

Originally posted by: BFG10K
Turn off vsync & AA and try again. Also make sure AGP is working properly (use the latest chipset drivers if it isn't).

If it still runs the same you are CPU limited.

First off vsync is off. Secondly if AA was on, on a 64bit memory bussed card, you wouldnt be seeing frames much at all on doom 3. The card scales as it should for such a crippled card. (except for this exception) In halo it decreases by 20% when i turn up the res for example. I also have the latest chipset drivers. They are the same ones i use on my own computer with my 9800p. I really dont think im making a mistake here with my testing.

Also an axp @ 2ghz clock shouldnt go down to 17fps twice on the timedemo. The benchmarks on any site do not compare to such lows. The game has the exact same minimums dispite the res. I'm really quite stumped by this issue. It seems as if the memory bus should be the limiting factor on doom 3 sense it is mostly video card bound. Its like either res or detail setting takes up the same amount of memory bandwidth. Any other ideas anyone?

 

[JBT]

Are you using timedemo demo 1 1 and adding the extra 1 on the end to make it precache the demo cause if not yeah it is going to run like crap no matter what comming right off the hard drive.

 

[Marsumane]

Originally posted by: JBT
Are you using timedemo demo 1 1 and adding the extra 1 on the end to make it precache the demo cause if not yeah it is going to run like crap no matter what comming right off the hard drive.

Yup. Ive ran it multiple times on both settings.

 

[Regs]

Sounds like a bottle neck. When you set your res that low you are putting all the work on the cpu. Then when you set it to 1024x768 you are spreading the work evenly across your system. 6600GT or better comes to mind.