NVIDIA GeForce GTX 970 has been one of the most popular graphics cards since the time of its release - all thanks to a very good ratio of performance, power consumption and of course the price. It turns out that this model has problems with the use of the full capacity of video memory.
NVIDIA’s GTX 980/970 using GM204 graphics core, the standard is a 256bit memory interface, 4GB of memory except that the GTX 980 has 16 sets of SMM unit and 13 set SMM unit in GTX 970. For the GTX 970, there are many players who have found a strange issue after testing lots of games – the GTX 970 can only use 3.5GB of memory, not utilizing 4GB of memory. Some people think that this is a bug, which eventually forward the matter to NVIDIA to explain NVIDIA GTX 970 graphics card memory configuration issues. This issue has also confirmed with a simple test by one of the forum members of ComputerBase, which checks the video memory bandwidth in blocks of 128 MB (application code is publicly available here ).
While the GeForce GTX 980 model – based on the same GPU is featuring a greater number of units and also hold 4GB of GDDR5 256-bit – the entire memory offers a very similar capacity. From the below screenshots you can see that GeForce GTX 970 list blocks are characterized by significantly worse outcomes.
NVIDIA GeForce GTX 970 uses only 3.5GB memory: NVIDIA answer
NVIDIA has released an official statement on this matter. It turns out that the GTX 970 is featuring special structure of the GPU die, which is slightly different from the model GeForce GTX 980. In GTX 970 GPU core memory is divided and available memory is in two sections with 3.5 GB and 0.5 GB – the first one has a higher priority in order to access to the layout, but if an application needs more than 3.5 GB of memory it will also access to the second segment. It means, if the memory occupied by the game size less than 3.5GB, then it will only access to first segment and if the game uses more memory (more than 3.5GB), then it will normally assess to both two parts.
Now if everyone understood the use of performance problems when its 0.5GB memory, the best detection method is performance testing. NVIDIA has made a real game test, by adjusting different settings, the test is as follows:
From the above performance test chart you can see that in the Shadow of Mordor game, memory occupancy in 3.5GB, GTX 980 performance is 72fps, the GTX 970 is 60fps. And when they low some settings GTX 980 talked to 55fps, GTX 970 down to 45fps. The loss of performance is only 1%. In the whole tests the gap between two is about 24% and 25%. Similarly, the performance gap in both Battlefield 4 is 3% and Call of Duty is also 4%.
NVIDIA said that this performance will have some impact on the graphics card, but compared with the GTX 980 the GTX 970 then actual impact is small of only 1-3%, which is not large.
NVIDIA little explanation for such technical issues here, although the GTX 970 describes why monitoring software only takes up 3.5GB of video memory to display “bug”, but did not specifically explain why “cross memory resource allocation system” will result in 3.5GB and 0.5GB differences.
NVIDIA recently released the GTX 960 using GM206 core, 8 groups SMM units, 128bit wide and 1024 CUDA core means utilizing the complete GM206 core. It will be difficult to say in the future to continue GM206 core (or open) More SMM units and launch new products, memory allocation, this problem may also occur again.