It appears that many users have been reporting all over the web of observed problems related to the GTX 970’s memory allocation. Basically, the problem has to do with the GTX 970 being unable to fully utilize 4GB of VRAM and when the last 500~700MB gets accessed, performance drops significantly. So far it seems to only affect the GTX 970 and the same problems have thankfully not popped up on the higher-end GTX 980 so this suggests that the problem is specifically GTX 970 hardware related and not related to the new Maxwell compression engine. The problem is also exceptionally noticeable in higher resolutions, for example in Far Cry 4, once memory usage exceeds 3400MB, framerates drop to single digits from 40-50 frames per second.
NVIDIA is aware of the problem and has responded to the users who have brought the topic up on the official GeForce forums, moderator ManuelG states: “We are still looking into this and will have an update as soon as possible.” We’ll look into the problem further with more testing and update when a solution (if any) has been found.
- GeForce forums: “GTX 970 3.5GB VRAM issue”
- Guru3D Forums:” GTX 970 VRAM allocation bug“
- Reddit: “GTX 960 Memory VRAM allocation”