GeForce GTX 970 memory allocation issue explained by Nvidia

[Scorpus]

Over the past few days it has emerged that the Nvidia GeForce GTX 970 might have a few issues addressing the entirety of its 4GB of VRAM. Posters on several enthusiast forums have been testing the card, and noticed that in some games it hits what appears to be a memory cap of 3.5 GB, leaving the last 512 MB empty even when the title may require it.

Furthermore, a synthetic benchmark was being used to test the memory bandwidth of each segment of the GTX 970's memory, and found that bandwidth dropped off significantly when the last 512 MB of the VRAM was being accessed. These issues were not present with the GTX 980, which features a fully-enabled GM204 core.

Some users were attributing micro-stutter while gaming in memory-intensive games to these VRAM issues. Others didn't notice any performance problems, and had no trouble getting games to use all of the card's 4 GB of memory. Now, Nvidia is offering up an explanation.

The GeForce GTX 970 is equipped with 4GB of dedicated graphics memory. However the 970 has a different configuration of SMs than the 980, and fewer crossbar resources to the memory system. To optimally manage memory traffic in this configuration, we segment graphics memory into a 3.5GB section and a 0.5GB section. The GPU has higher priority access to the 3.5GB section. When a game needs less than 3.5GB of video memory per draw command then it will only access the first partition, and 3rd party applications that measure memory usage will report 3.5GB of memory in use on GTX 970, but may report more for GTX 980 if there is more memory used by other commands. When a game requires more than 3.5GB of memory then we use both segments.

The statement goes on to compare the performance of a GTX 970 to a GTX 980 in memory intensive applications.

Game and Settings	GTX 980	GTX 970
Shadows of Mordor
<3.5GB setting = 2688x1512 Very High	72fps	60fps
>3.5GB setting = 3456x1944	55fps (-24%)	45fps (-25%)
Battlefield 4
<3.5GB setting = 3840x2160 2xMSAA	36fps	30fps
>3.5GB setting = 3840x2160 135% res	19fps (-47%)	15fps (-50%)
Call of Duty: Advanced Warfare
<3.5GB setting = 3840x2160 FSMAA T2x, Supersampling off	82fps	71fps
>3.5GB setting = 3840x2160 FSMAA T2x, Supersampling on	48fps (-41%)	40fps (-44%)

According to their performance data, there is very little difference in performance between the GTX 970 and GTX 980 when the last 512 MB of memory has been allocated, despite the differences in their memory systems. This last 512 MB is the portion of memory that was supposed to be cripplingly slow, or even unavailable to some users.

Of course Nvidia's data might not be telling the full story, and there definitely could be some issues related to the paritioning of VRAM, most notably stuttering which is not conveyed in average frame rate figures. We'll have to wait until someone does a full frame time analysis before the issue can be explored further.

Permalink to story.

https://www.techspot.com/news/59509-geforce-gtx-970-memory-allocation-issue-explained.html

 

[genuinethief]

http://megagames.com/news/bug-geforce-970-makes-last-700-mb-ram-slow-crawl

I plan to get a gtx 970.

 

[Guest]

Oh this is typical. I decided to get one, its sat in its box un opened atm. 2 days later the 960's come out at a more wallet friendly price, and now I read this. Well tits... I probably won't notice anything I'm not a hardcore nerd.

 

[Deltree]

I guess I don't understand why an additional VRAM partition is needed. I don't partition my HDD because I don't need a virtual speration of my physical drive. If I need a new drive, a new physical drive is added. To segment that seems pointless to me at my user level. I dont see any benefit to partitioning besides posssibly hiding system files from a user that may potentially delete or move important system files through being uneducated about the proper usage of expensive equipment they own. ("Whatever you do, don't touch D:\ System.") Unless I am web browsing, I am editing HD video or gaming. In my opinion, either I need basically no GPU for browsing, or everything my GPU has got for edits and gaming. I don't feel like I need some mathed out curve adjusting the power, fan speed, clock speed, VRAM speed, and now (I guess) which of my VRAM partitions are being utilized if this is going to negatively affect my performance. Does anyone else need half speed from their components? Need it enough to bring down your top end performance? Not me. But I am no pro, and probably don't know better than Nvidia who makes GPUs, while so far the nuber of GPUs I have made is zero.

 

[Guest]

I don't partition my HDD because I don't need a virtual speration of my physical drive. If I need a new drive, a new physical drive is added. To segment that seems pointless to me at my user level. I dont see any benefit to partitioning besides posssibly hiding system files from a user that may potentially delete or move important system files through being uneducated about the proper usage of expensive equipment they own.

Partitioning the hard drive is a huge help when reinstalling your OS, for example. If you keep your OS in one partition and your bulk personal data (music, photos, videos, documents) in another, all you need to do is format the OS partition and your data is left untouched.
Or you can also just create a temporary partition to store your data and merge it back after reinstalling the OS, so you can format your PC without needing external backup devices.

 

[Guest]

Well from the article my first un intelligent impression was that the 970 partitioned has the glitchy and doesnt perform like the 980 which isnt partitioned, so unpartitioning (er dumb?) and it makes it run a bit more like the 980...
so they partition it to make it that extra bit inferior ? or they did something wrong ? sounds like I should send mine back now

 

[hahahanoobs]

If nVIDIA has to disable this partition to assure a smooth experience, I'm okay with that... this time. I will be watching to see how all this plays out.

Edit:
Our own Josh Walrath (pcper.com) offers this analysis:

A few days ago when we were presented with evidence of the 970 not fully utilizing all 4 GB of memory, I theorized that it had to do with the reduction of SMM units. It makes sense from an efficiency standpoint to perhaps "hard code" memory addresses for each SMM. The thought behind that would be that 4 GB of memory is a huge amount of a video card, and the potential performance gains of a more flexible system would be pretty minimal.

I believe that the memory controller is working as intended and not a bug. When designing a large GPU, there will invariably be compromises made. From all indications NVIDIA decided to save time, die size, and power by simplifying the memory controller and crossbar setup. These things have a direct impact on time to market and power efficiency. NVIDIA probably figured that a couple percentage of performance lost was outweighed by the added complexity, power consumption, and engineering resources that it would have taken to gain those few percentage points back.

Maxwell is a different beast, and Josh is a smart guy (he suspected what nVIDIA later (confirmed?)), so unless I notice abnormalities with framerate and/or freezing or crashing while gaming, this is a non issue for me.

 

[Nero7]

Does this affect the 770 as well?

 

[wastedkill]

According to hahahanoobs hes okay with buying a broken or in nvidias case it looks like a product with an illegal false advertising on top.

If you put 2 memory segments which is the worlds first for your company and it destroys your 2ndary sole revenue pushing product then you got a big problem, I see 2 outcomes to this, fix it without replacing your customers broken products or replace your customers broken products with one thats fully functioning.

Or nvidia could go the other route give them a refund based on the performance drop when fully using the graphics cards which from looks of this article seems to be a hefty amount.

 

[hahahanoobs]

According to hahahanoobs hes okay with buying a broken or in nvidias case it looks like a product with an illegal false advertising on top.

If you put 2 memory segments which is the worlds first for your company and it destroys your 2ndary sole revenue pushing product then you got a big problem, I see 2 outcomes to this, fix it without replacing your customers broken products or replace your customers broken products with one thats fully functioning.

Or nvidia could go the other route give them a refund based on the performance drop when fully using the graphics cards which from looks of this article seems to be a hefty amount.

So your issue is with the "false advertising?" It does have 4GB so that's petty, but ok. Sure they could of put 3 or 3.5GB on the box, but we all still would of bought it anyway. The REAL issue is, does this the VRAM allocation affect performance in games and so far, in my case anyway, the answer is no.

 

[VitalyT]

Looks and sounds like an artificial performance corking - make a perfectly good product, but if turns out to be too good - castrate it a little.

 

[wastedkill]

So your issue is with the "false advertising?" It does have 4GB so that's petty, but ok. Sure they could of put 3 or 3.5GB on the box, but we all still would of bought it anyway. The REAL issue is, does this the VRAM allocation affect performance in games and so far, in my case anyway, the answer is no.

Depends on the games you play but I know for me I have definately noticed it and looking at other sites so have plenty of others.

 

[LNCPapa]

Just curious - what games have you noticed it in? I want to do some focused testing myself.

 

[hahahanoobs]

Depends on the games you play but I know for me I have definately noticed it and looking at other sites so have plenty of others.

Let me know how your progress goes with getting that refund any time soon.

 

[Deltree]

I don't partition my HDD because I don't need a virtual speration of my physical drive. If I need a new drive, a new physical drive is added. To segment that seems pointless to me at my user level. I dont see any benefit to partitioning besides posssibly hiding system files from a user that may potentially delete or move important system files through being uneducated about the proper usage of expensive equipment they own.

Partitioning the hard drive is a huge help when reinstalling your OS, for example. If you keep your OS in one partition and your bulk personal data (music, photos, videos, documents) in another, all you need to do is format the OS partition and your data is left untouched.
Or you can also just create a temporary partition to store your data and merge it back after reinstalling the OS, so you can format your PC without needing external backup devices.

I can see how that could be a huge help if you don't have backup external drives to use, but I do and like the ease of plugging something into my usb port and backing up my ish compared to creating and managing or deleting partitions. I rarely format my PC.

 

[martinron]

Oh this is typical. I decided to get one, its sat in its box un opened atm. 2 days later the 960's come out at a more wallet friendly price, and now I read this. Well tits... I probably won't notice anything I'm not a hardcore nerd.

so why would you buy a 970 then? People paid allot of money for this card. And people have every right to get their money back. I personally will never buy Nvidia again and am sure many-many people feel the same way if Nvidia do not fix this problem or refund people their money back

 

[dividebyzero]

Or nvidia could go the other route give them a refund based on the performance drop when fully using the graphics cards which from looks of this article seems to be a hefty amount.

The performance drop is actually commensurate with the difference in hardware. Aside from the obvious 20% drop in each of the texture address units, cores, and SM's, Nvidia's internal architecture leads to further disparity.

 

[Scorpus]

Does this affect the 770 as well?

No, just the GTX 970 as far as we're aware

 

[Guest]

I doubt we'll get refunds for the computers that used to come with "500 GB" harddrives that were in the 400s

 

[trgz]

I don't partition my HDD because I don't need a virtual speration of my physical drive. If I need a new drive, a new physical drive is added. To segment that seems pointless to me at my user level. I dont see any benefit to partitioning besides posssibly hiding system files from a user that may potentially delete or move important system files through being uneducated about the proper usage of expensive equipment they own.

Partitioning the hard drive is a huge help when reinstalling your OS, for example. If you keep your OS in one partition and your bulk personal data (music, photos, videos, documents) in another, all you need to do is format the OS partition and your data is left untouched.
Or you can also just create a temporary partition to store your data and merge it back after reinstalling the OS, so you can format your PC without needing external backup devices.

Yup, even with my 5 HDD & 1 SDD setup (1x1TB, 2x512GB, 2x250GB and 120GB SSD) , I have 13 partitions to make defragging the HDDs easier; allowing portability when upgrading the OS etc; double/triple booting; a dedicated partition on the outside edge of one HDD for a swap file; SSD backups; and housekeeping ie keeping the documents (mp3s, photos, databases, programming work) separate from the games. Even though the games are generally on the outside partition, I do go further and use Ultimate Defrag to organise more intensive games/programs to the outer edges of them - admittedly if I simply had 1xSSD and 2x1TB HDDs I'd probably partition each 1xTB into three chunks

 

[trgz]

...and I like my GTX 970

 

[AlanCasseb]

I don't partition my HDD because I don't need a virtual speration of my physical drive. If I need a new drive, a new physical drive is added. To segment that seems pointless to me at my user level. I dont see any benefit to partitioning besides posssibly hiding system files from a user that may potentially delete or move important system files through being uneducated about the proper usage of expensive equipment they own.

Partitioning the hard drive is a huge help when reinstalling your OS, for example. If you keep your OS in one partition and your bulk personal data (music, photos, videos, documents) in another, all you need to do is format the OS partition and your data is left untouched.
Or you can also just create a temporary partition to store your data and merge it back after reinstalling the OS, so you can format your PC without needing external backup devices.

Yup, even with my 5 HDD & 1 SDD setup (1x1TB, 2x512GB, 2x250GB and 120GB SSD) , I have 13 partitions to make defragging the HDDs easier; allowing portability when upgrading the OS etc; double/triple booting; a dedicated partition on the outside edge of one HDD for a swap file; SSD backups; and housekeeping ie keeping the documents (mp3s, photos, databases, programming work) separate from the games. Even though the games are generally on the outside partition, I do go further and use Ultimate Defrag to organise more intensive games/programs to the outer edges of them - admittedly if I simply had 1xSSD and 2x1TB HDDs I'd probably partition each 1xTB into three chunks

Have u met FOLDERS?

 

[Guest]

Just go read Tweakguides.com, it's already been tested by the author of the site. He knows his stuff. He says while there maybe time whens the 4GB isn't fully used, there is no performance impact should would affect the user. So whether your using 3.5 or the full 4GB, there isn't anything people should worry about. He found no significant performance issue like some people have claimed. So that means no hitching or longer pauses were found. Just go to the site and read what he wrote, it's right on the home page.

 

[trgz]

Just go read Tweakguides.com, it's already been tested by the author of the site. He knows his stuff. He says while there maybe time whens the 4GB isn't fully used, there is no performance impact should would affect the user. So whether your using 3.5 or the full 4GB, there isn't anything people should worry about. He found no significant performance issue like some people have claimed. So that means no hitching or longer pauses were found. Just go to the site and read what he wrote, it's right on the home page.

A voice of sanity

 

[hahahanoobs]

Update:
NVIDIA's Jonah Alben, SVP of GPU Engineering has gone into greater detail about the issue. He also revealed some info about the actual specs of our GTX 970's.

Did nVIDIA eff up? Yes they did.
Will I be returning my card as of this moment? No.
Will I be more cautious in the future? Yes!