Last week, commenters on NVIDIA's forums, reddit, Guru3D and elsewhere started digging into what looked to be a concerning problem: the GeForce GTX 970 only seems to use 3.5GB of its 4GB of VRAM. Few games can really utilize 4GB of VRAM, but some commenters noted a serious drop in performance or stuttering when pushing the GTX 970 over the 3.5GB threshold. The same problem did not appear to affect the GTX 980.
Re: Why NVIDIA's GTX 970 slows down when using more than 3.5GB VRAM
Yes, that last 0.5GB of memory on your GeForce GTX 970 does run slower than the first 3.5GB. More interesting than that fact is the reason why it does, and why the result is better than you might have otherwise expected. Last night we got a chance to talk with NVIDIA's Senior VP of GPU Engineering, Jonah Alben on this specific concern and got a detailed explanation to why gamers are seeing what they are seeing along with new disclosures on the architecture of the GM204 version of Maxwell.
UPDATE 1/28/15 @ 10:25am ET: NVIDIA has posted in its official GeForce.com forums that they are working on a driver update to help alleviate memory performance issues in the GTX 970 and that they will "help out" those users looking to get a refund or exchange.
Re: Why NVIDIA's GTX 970 slows down when using more than 3.5GB VRAM
On forums near and far, there have been reports users have been experiencing memory allocation issues on NVIDIA's GTX 970. Much of this centered around the fact that certain applications showed the GTX 970 to be utilizing just 3.5GB of its supposed 4GB of memory even though the GTX 980 and other cards showed their full memory layout as being accessible. There were further reports that once the 3.5GB threshold was surpassed, the GTX 970 suddenly exhibited a drastic loss of performance. It looked suspiciously like NVIDIA's price / performance darling wasn't able to physically communicate with its advertised memory allotment and if communication was taking place, that bandwidth was somehow truncated.
Naturally, this sparked a large number of theories regarding the Maxwell architecture, its abilities and how NVIDIA has allocated resources on their $350 graphics card. NVIDIA themselves have now stepped in, trying to set the record straight. What follows is a simplified version of our technical briefing with them alongside some basic benchmarks.
Re: Why NVIDIA's GTX 970 slows down when using more than 3.5GB VRAM
A while ago we already reported that a legal company was homing in on Nvidia die to the GTX 970 Memory Debacle. Over the weekend it has become clear that in the state of California owners of a GTX 970 have filed a class-action lawsuit in a US Court (District Court for the Northern District of California).
The lawsuit, titled "Andrew Ostrowsky (and others in similar situation) vs. NVIDIA Corporation and GIGABYTE Global Business Corporation", which is accusedof unfair, unlawful, and deceptive business practices, in three separate charges, and misleading advertising, demanding for Jury Trial. Nvidia markets the chip as having 4GB of performance-boosting video RAM, but some users have complained the chip falters after using 3.5GB of that allocation.
