GTX 970s can only use 3.5GB of 4GB VRAM issue - Overclock.net - An Overclocking Community

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GTX 970s can only use 3.5GB of 4GB VRAM issue

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post #1 of 2990 (permalink) Old 01-11-2015, 07:32 PM - Thread Starter
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"Going beyond 3.5GB vram usage ... severely degrades the performance, as if the last 512mb is actually being swapped from the RAM."

980 works fine in comparison.

Guru3D thread here:
here

Reddit hardware thread:
here

Reddit PC Gaming thread:
here

Example:
In Far Cry 4 @ 1440p
No AA: 3320MB Max Vram, locked at 60 fps
2x MSAA: 3405MB Max Vram, locked at 60fps
4x MSAA: 3500MB Max Vram, 45-60fps
8x MSAA, starts around 3700-3800MB @ 4-5fps, stabilizes at 3500MB @ 30-40fps.

Xeon Hexa @ 4.2 GHz, Asus P6T Deluxe V2, 12GB RAM, 2x GTX 970 4GB SLI @ +17% OC, Quad-SSD RevoDrive3 x2 240GB, 10x 15Krpm U320 SCSI RAID0 @ PCIe x4, Modded X-Fi, Dual 1000W PSUs, 2x 2000W ButtKicker LFE, Sennheiser HD650, Stereo3D Projector with Shutter Glasses.
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post #2 of 2990 (permalink) Old 01-11-2015, 07:38 PM
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post #3 of 2990 (permalink) Old 01-11-2015, 07:38 PM
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Hmm.. i must say that i have never seen mine reaching 4GB just yet.

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post #4 of 2990 (permalink) Old 01-11-2015, 08:13 PM
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I have Far Cry 4 up and running in 5760x1080.

with no AA im getting 3602 to 3700ish. i even saw it hit the 3800's

2xMSAA, the low went to 3675, but still about the same as no aa

keep in mind, i did see it go down to 3500 on both settings in calmer areas.

anything above that was completely unplayable.

edit:
this is with 2 in SLI

and with no AA im getting 60-80fps, 2xMSAA 45-60fps area
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post #5 of 2990 (permalink) Old 01-11-2015, 08:15 PM
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Just tried on Siege on BF4.

I usually run 150% and 2xMSAA which gives ~2700MB usage. Bumped this to 200% and 4xMSAA and it ran at 3300-3400MB, but that's as high as I could get it.

Just to confirm this thread is about lower performance after going >3500MB right? Not that the cards can't actually do >3500MB?


"We must let go of the life we have planned, so as to accept the one that is waiting for us."


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post #6 of 2990 (permalink) Old 01-11-2015, 08:22 PM
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Quote:
Originally Posted by error-id10t View Post

Just tried on Siege on BF4.

I usually run 150% and 2xMSAA which gives ~2700MB usage. Bumped this to 200% and 4xMSAA and it ran at 3300-3400MB, but that's as high as I could get it.

Just to confirm this thread is about lower performance after going >3500MB right? Not that the cards can't actually do >3500MB?

Its the cards aren't playable above 3500.

but mine seam to have a 3800 cap, then the fps go to the sub 5-10 range.
maybe is just the 5760x1080 res.

i noticed i forgot to mention my fps in my first post, but i fixed it.
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post #7 of 2990 (permalink) Old 01-12-2015, 02:12 AM
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I´m having the same problem, the ram consumption barely goes above 3.6GB and when it does i get massive stuttering, the biggets ofender is COD:AW, as soon as it goes beyond 3.6GB it stuters like hell even with high framerates.

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post #8 of 2990 (permalink) Old 01-12-2015, 02:57 AM
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I didn't believe this at first, but I just decided to try and test it myself with texture modded Skyrim and my SLI 970s. I tried to push the 3.5 GBs barrier by downsampling it from 5120x2880 with the four following experimental conditions:

1. No MSAA applied on top

2. 2xMSAA applied on top

3. 4xMSAA applied on top

4. 8xMSAA applied on top



Since MSAA is known to be VRAM heavy, it made sense. I also kept a close eye on GPU usage and FPS with the Rivatuner overlay as well as VRAM usage. All of this was done running around Whiterun to minimize GPU usage. My results were as follows.

1. Skyrim peaked at about 3600 MBs in usage with occasional brief hitching while loading new textures in and out of VRAM. GPU usage remained well below 99% on each card.

2. Skyrim once again peaked at about 3600 MBs with the mentioned hitching, this time somewhat more frequently. Once again, GPU usage remained well below 99%.

3. Skyrim yet again peaked at about 3600 MBs and hitched much more prominently and frequently at the same time as VRAM usage droppped down 100-200 MBs. GPU usage was below 99% again with FPS still at 60 aside from those hitches.

4. Now Skyrim was using the full 4 GB framebuffer with massive stuttering and hitching from a lack of VRAM. This time, I had to stare at the ground to keep GPU usage below 99% and retain 60 FPS. I ran around Whiterun just staring at the ground and it remained at 60 FPS except with those massive hitches where GPU usage and framerate temporarily plummeted. This last run merely indicated that Skyrim can indeed use more VRAM than it was with the previous 3 settings and so the issue seems to be with the 970s themselves rather than just the game in this example. The performance degradation aside from VRAM was severe, but that could just be 8xMSAA at 5K taking its calculative toll.




So it seems to me that my 970s refuse to utilize above ~3600 MBs of VRAM unless they absolutely need it, but I've no idea why. Nvidia didn't gimp the memory bus in any overly obvious way from the full GM204 chip therefore the 970s should have no issue using the same VRAM amount as the 980s. I don't like what I see, it's like the situation with the GTX 660 that had 2 GBs but could only effectively use up 1.5 without reducing its bandwidth to a third, so it tried to avoid exceeding 1.5. The difference is that was predictable due to the GK106's 192-bit memory bus, there's nothing about the 970's explicit specifications that indicates the same situation should apply.

A similar shortcoming was noticed sometime back regarding the 970's ROPs and how the cutting-down of 3 of GM204's 16 SMM units affected the effective pixel fillrate of the 970s despite retaining the full 64 ROPs. It's possible that Maxwell is more tightly-connected to shader clusters and severing them affects a lot about how the chip behaves, but that doesn't really make sense. If this is an issue, it's almost certainly software-related. I'm not happy regardless of the reason and I'll try more games later. Anecdotally, I have noticed recent demanding games peaking at about 3500-3600 MBs and can't actually recall anything going beyond that. I didn't pay attention to it or change any conditions to test it.

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post #9 of 2990 (permalink) Old 01-12-2015, 03:07 AM
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Why do people keep making this same thread when it has been disproven...

Go play something like Lords of the Fallen and post results. Others including myself have and posted the results in the official 970 thread and others have done this more in depth tests on other forums.

It's simple, some games are currently programmed to use more or all and some aren't at this point in time.
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post #10 of 2990 (permalink) Old 01-12-2015, 03:10 AM
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interesting results, subbed.

Originally Posted by flyingsaucers

Cue 20 pages of repetitive whining about CoD. Gotta love OCN CoD threads. Every single one is the same. Page after page of the same haters, spewing the same recycled criticism about CoD games. We get it, guys. We know you don't like the games.
Here's a real brain teaser - you all keep criticizing Treyarch & Infinity Ward for their lack of originality in CoD games, yet it's perfectly okay to spawn 20 page threads of repetitive whining every time somebody posts about CoD in the news section! See the irony? No? Of course not. Carry on, then.
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