I’ve never been a conspiracy theorist: I believe human greed and stupidity are simple explanations for all that’s wrong in the world, and that we don’t need to concoct a shadowy Illuminati organization to take the blame. In this case it’s understandable: how does a highly technical team of GPU experts, one that works directly for the chipmaker, make such a huge mistake? It’s times like these that conspiracy theories begin to fly. The company claims this is the result of a misunderstanding on the part of the technical marketing team, which was not aware of the partially-enabled ROP cluster, and that the issue was not identified internally until this month when people began digging into the memory issue.
This is less than the 64 ROPs and 2 MB of L2 that Nvidia originally indicated in its press materials. As a result, there are 56 functional ROPs in the GeForce GTX 970, and the chip has access to 1.75 MB of L2 cache. In addition, an eighth of the L2 cache is not used. We will keep an eye out for it and be able to call it out now that we know the actual specifications, but none of this new information invalidates the benchmark results we've already collected. There are probably some particular situations that will expose this weakness, but it is surprisingly difficult to create this scenario. As a result the 3.5 GB portion can be accessed with 196 GB/s of bandwidth, while the 512 MB portion has 28 GB/s of bandwidth available.
In this way, all 4 GB of RAM is usable, although segmented. With one-eighth of the ROP partitions disabled, one-eighth of the memory (512MB) must be accessed in a special way, through the working half of the partition. That partially disabled partition is responsible for the strange 3.5GB/512MB memory split, as memory controller resources are linked through them. Note that one of the four ROP partitions is not fully enabled, but partially disabled. It remains to be seen if this technique causes any notable performance detriment in a real-world scenario, but from what we've seen so far, it does not.īut why is there an odd split in memory resources in the first place? It turns out, this is a clue that hints at the real issue: Nvidia’s incorrect reporting of the GeForce GTX 970’s technical specifications and GM204 GPU resources. It is accessed differently and with different theoretical bandwidth, but it's all there and available.
NVIDIA GTX 680 VS 970 FULL
Yes, the card has access to a full 4GB of RAM. It turns out that this is a symptom of memory segmentation, as the card splits the 4GB into a 3.5GB high-priority segment and a 512MB low-priority segment. This issue reared its head when some users noted that in certain cases the GeForce GTX 970 reported 3.5GB of graphics memory despite being sold as a 4GB card.