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VRAM usage bogs down CPU?

#1JonWood007Posted 7/22/2014 9:37:20 AM
Ok, something I've been finding since messing with various GPUs in the last couple weeks, the more I notice that VRAM usage really kills my performance, especially in BF4.

Several weeks ago, my 580 died. Most of you know this. I always had problems with games like BF4 and Crysis 3 on my 580, getting unstable performance with low framerates. I didn't max out my vram usage, in the case of BF4 my GPU wasnt even being used full throttle, and when I brought up the graph in BF4, it clearly showed a very severe CPU bottleneck when running on mostly high/ultra settings. I ran high textures because I literally maxed my VRAM with ultra, and that helped performance a bit.

Then, my 580 died, and I returned to using my HD 5850 until EVGA sent me the replacement I got (760 superclocked). I turned textures down to low, only having 1 GB of VRAM and all, and my framerates went through the roof. I went from dipping down to 25-30 FPS in parts of crysis 3 and BF4 to running BF4 at 45+ and crysis 3 at 60+.

So then I got my GTX 760 SC. I cranked everything up to ultra again, and in the last few days, performance started to act like my 580 in Crysis 3 and BF4. I started getting dips, and despite running ultra textures in both games, I was only using 1.6 GB of my VRAM.

I turned textures down to high in Crysis 3, which was the trick I learned on my 5850, and the dips went away. I recently tried the same in BF4, and the same thing happened. I turned everything I had at ultra to high, and boom, now I'm going from abou 50 average with dips down to 30, to 70 FPS average with dips down to 40-45. Looking at the graph, my CPU bottleneck appears to be gone as well.

I can't say for certain, but seeing how in BF4 in particular I already lowered settings I know to be heavily CPU dependent like lighting and mesh to low, it seems strange how lowering settings, particularly tectures (that seems to be the big one) can cause so much strain on my CPU. But the data is clear. I turn that stuff to ultra, a CPU bottleneck happens.

For the record, when messing with my 580 on Planetside 2, the same thing happened. Planetside 2 is HEAVILY CPU dependent, yet despite not maxing VRAM, turhning textures to ultra always killed it (on the other hand the 760SC runs ultra textures fine).

I know nothing is wrong with the card, because I noticed this behavior on all 3 GPUs I've owned. On my 1 GB VRAM 5850, I had to run textures for these games on low. On my 580, I'm guessing I'd have to run medium to get them to work properly. With my 760, I can run them on high. The thing is, on all of these cards, I'm not even maxing the VRAM and the performance goes to crap anyway.
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Desktop: Phenom II X4 965 | 8 GB DDR3 | GTX 760 SC | 1 TB HDD | W7 | 650W Antec | 1600x900
Laptop: A6 3400m | 4 GB DDR3 | HD 6520g | 500 GB HDD | W7 | 1366x768
#2SinisterSlayPosted 7/22/2014 9:43:40 AM
If your run out of video memory for textures, then system memory is used instead and that is only accessible through the CPU so it is much slower.
And you won't necessarily show all your memory used as some will be reserved for the frame flips.
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He who stumbles around in darkness with a stick is blind. But he who... sticks out in darkness... is... fluorescent! - Brother Silence
#3JonWood007(Topic Creator)Posted 7/22/2014 9:44:41 AM
Also, linking it to "VRAM" usage might be a misnomer. It seems to be linked to texture settings. On ultra textures (or high, if we're talking my 580, or even medium talking about my 5850 in the games in question), textures bog the game down to all heck....but going one notch down makes the game run smooth as butter. In BF4, to summarize...on ultra, I seem to be getting a major CPU bottleneck looking at the graph you can bring up via commands, but on high texture settings, the FPS is much higher, the game way smoother, and the CPU bottleneck seems to disappear.

It's just very strange. I always thought textures were wholly dependent on your GPU, and VRAM usage. It's strange to see the games bog down on multiple cards when I ain't even maxing out my vram.
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Desktop: Phenom II X4 965 | 8 GB DDR3 | GTX 760 SC | 1 TB HDD | W7 | 650W Antec | 1600x900
Laptop: A6 3400m | 4 GB DDR3 | HD 6520g | 500 GB HDD | W7 | 1366x768
#4wildog2006Posted 7/22/2014 9:45:31 AM
So you're saying that lower settings in games let them run better? Who would have guessed...
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London-SV on Throttle Control in Gran Turismo 6 ~ ''Unless you're flooring it at every opportunity... Try to be a little more genital on the accelerator''
#5JonWood007(Topic Creator)Posted 7/22/2014 9:47:48 AM
Ok? But the thing is, i'm not even maxing out my VRAM. I was only using 1.6-1.7 GB in both crysis 3 and BF4 on ultra.

On high I'm down to 1.2-1.3....I can understand it bogging down when I'm above 1.8 or so...I just think it's strange when i have several hundred MBs of VRAM to spare and the game starts running badly. I guess it makes sense tho...
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Desktop: Phenom II X4 965 | 8 GB DDR3 | GTX 760 SC | 1 TB HDD | W7 | 650W Antec | 1600x900
Laptop: A6 3400m | 4 GB DDR3 | HD 6520g | 500 GB HDD | W7 | 1366x768
#6JonWood007(Topic Creator)Posted 7/22/2014 9:48:21 AM
Texture settings, yes. In games that maxed out don't even use my whole 2 GB VRAM...
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Desktop: Phenom II X4 965 | 8 GB DDR3 | GTX 760 SC | 1 TB HDD | W7 | 650W Antec | 1600x900
Laptop: A6 3400m | 4 GB DDR3 | HD 6520g | 500 GB HDD | W7 | 1366x768
#7SinisterSlayPosted 7/22/2014 11:56:50 AM
JonWood007 posted...
Texture settings, yes. In games that maxed out don't even use my whole 2 GB VRAM...


SinisterSlay posted...

And you won't necessarily show all your memory used as some will be reserved for the frame flips.

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He who stumbles around in darkness with a stick is blind. But he who... sticks out in darkness... is... fluorescent! - Brother Silence