Nvidia explains the GTX 970's memory 'problems'

[watercooled]

Problem is games like Shadow of Mordor and Advanced Warfare that will use as much video RAM is available to them. I wonder if it would be beneficial then to appear as a 3.5GB card to those games? With dual-channel DDR3-1600 (or triple DDR3-1066) you've got 25.6GB/s total bandwidth on the system memory, so it could actually be faster for textures etc to spill over into system memory than use that last 512MB GDDR5 running at 20GB/s. I think either is going to hurt performance a lot more than nVIDIA suggests though.

That last 512 can only run at max speed if nothing is accessing the adjacent memory channel; I've no idea how it's prioritised but as I said in an earlier post, in theory it could end up being far lower than even that. You're looking at a maximum possible 28GB/s aggregate bandwidth, so 50:50 that's 14GB/s per channel, assuming interleaving with no additional overhead.

Can someone indulge my curiosity - how common is it for a current game title to request that full 4GB? Or are games these days programmed to ram (no pun intended) as much texture info into the GDDR as possible in a caching arrangement. I'm not a 970 owner (and after this I've no intention of being) so it is really just idle curiosity on my part.

A lot of modern games try to use all VRAM available for e.g. caching; apparently it's down to Nvidia's driver to try to figure out what should go where as the process needs to be transparent to games, and as it stands there isn't really an alternative as games and D3D have no understanding of asymmetrical VRAM speeds AFAIK and nor would it help as the driver/OS are the ones responsible for memory management.

As long as the driver tells a game there's 4GB to use, the game can only assume it's equal, so a lot of weight is put on the driver to predict correctly.

[shaithis]

A lot of modern games try to use all VRAM available for e.g. caching; apparently it's down to Nvidia's driver to try to figure out what should go where as the process needs to be transparent to games, and as it stands there isn't really an alternative as games and D3D have no understanding of asymmetrical VRAM speeds

I guess some of the terrible console ports will show this up, which is unfortunate. I am guessing nVidia will add optimisations into new drivers to combat it though.

Would be good if some of these games (like SoM and CoD:AW) actually made decent use of the VRAM they take. I do find it highly perplexing how those titles are using the VRAM they are....and they seem to be the biggest culprits.

[watercooled]

It's something the devs haven't had to worry about before, so there was no reason to stop short of using all VRAM, as it's much faster for caching than fetching from main memory even if they're not actively using it. And just filling the memory, even with caches, it seems can push sensitive parts of memory into the bottleneck. That's not on the game developers, regardless of how (in)efficiently they're loading VRAM.

It's loosely similar to how some applications suffered with hyperthreading enabled, mainly on older OSes without fully SMT-aware schedulers. Even if the application developers were fully aware there's not much they could have done as its down to the OS to assign threads properly. The devs had likely gone to a lot of trouble to ensure good threading in their code (to make good use of the hardware available, much as how game devs now are making use of available VRAM) but because the OS was treating SMT cores as real cores, it could destroy performance. The VM issue I mentioned earlier is an extreme example. I remember some instances of game stuttering could be solved by disabling Hyperthreading.

[shaithis]

It's something the devs haven't had to worry about before, so there was no reason to stop short of using all VRAM, as it's much faster for caching than fetching from main memory even if they're not actively using it. And just filling the memory, even with caches, it seems can push sensitive parts of memory into the bottleneck. That's not on the game developers, regardless of how (in)efficiently they're loading VRAM.

What I am talking about, is the devs/port.

SoM, ultra textures requires 4GB VRAM (it tells you this when selecting the option). Play the game with ultra textures and tell me it looks like it needs 4GB of VRAM. The textures are absolutely awful and still look very low resolution. It's the same story with the new CoD.

Funny how both these titles are causing the most issues......and both seem to "need" VRAM for no good reason that I can see.

[jigger]

So when are Nvidia offering refunds?

[jigger]

My friend got refused an RMA as no fault found, even though at times the chokes on the card sound like a 56K modem.

[gwp]

Nvidia is refunding cards

http://hardforum.com/showthread.php?t=1849838&page=15

see post 287

[HalloweenJack]

if the ram gives an effective 22GB/s then system ram has higher bandwidth:

http://www.techspot.com/review/837-i...yon/page2.html

[kalniel]

if the ram gives an effective 22GB/s then system ram has higher bandwidth:

http://www.techspot.com/review/837-i...yon/page2.html

Presumably that's the direct RAM to CPU bandwidth. PCIe probably has slower access to system RAM as it has to go across PCIe and through the CPU.

Assuming 16x PCIe 2.0 lanes, it's something like 8GB/s through PCIe.

[MrJim]

Gotta love competition, eh?

[shaithis]

Gotta love competition, eh?

The joke is, most people don't need that much VRAM and AMD cards need more for Mantle anyway.

[watercooled]

Oh dear is that an official AMD thing? I caught a glimpse of it yesterday and thought it was a spoof.

@shaithis: The issue isn't really about the amount of memory, it's part of it being far slower which is causing issues, the card simply having 3.5GB at full speed would probably not have caused these problems. Perhaps future drivers will be more careful in allowing use of the last 512MB unless they have a solid profile for the game.

[gwp]

Nvidia is apparently deleting posts from their Geforce forum thread

https://forums.geforce.com/default/topic/803518/geforce-900-series/gtx-970-3-5gb-vram-issue/

and they've deleted all the comments from their product page

http://www.geforce.com/whats-new/articles/maxwell-architecture-gtx-980-970

[shaithis]

@shaithis: The issue isn't really about the amount of memory, it's part of it being far slower which is causing issues, the card simply having 3.5GB at full speed would probably not have caused these problems. Perhaps future drivers will be more careful in allowing use of the last 512MB unless they have a solid profile for the game.

I fully understand that, I just found it ironic that the joke image talks about when "4GB means 4GB"...when its the AMD cards that need more VRAM.

99% of 970 owners wouldn't notice the missing ram if they disabled it, hell I doubt many 4GB AMD card owners use half their VRAM.

[watercooled]

when its the AMD cards that need more VRAM.

They do?

[spl]

That's pretty low AMD trying to muddy the waters and mislead people to think that there's actually not 4GB installed on the cards. That being said, it could end up as only 3.5GB usable if a driver / BIOS update does disable the last 512MB (which could be the best solution if we can't stop games expanding into that space unless they absolutely have to).