Testing memory bandwidth on video cards is tricky, but we’ve been dabbling around testing it in recent weeks. We built a new system to test just memory bandwidth it is best the test on a system that has a CPU with integrated graphics in order for the discrete graphics card can be run in headless mode. We also disabled Windows Aero and set the system to high performance mode for both the display settings and power settings. Nai’s GPU memory bandwidth test only works on NVIDIA CUDA cards, so we tested a handful of NVIDIA GeForce GTX reference cards from the Fermi, Kepler and Maxwell series to see how they perform. The ASUS STRIX 950 2GB and ASUS STRIX 960 2GB video cards are the only non-reference cards in the chart below.
We weren’t expecting to reach the theoretical peak bandwidth figures, but all of the cards came in reasonably close. The NVIDIA GeForce GTX 950 is rated as have 105.8 GB/s of memory bandwidth and we averaged 98.0 GB/s across the 2GB frame buffer.
We are really shocked that the NVIDIA GeForce GTX 950 had higher memory bandwidth than the GForce GTX 960! We tested the NVIDIA GeForce GTX 960 with GeForce 355.60 and the GeForce GTX 950 with GeForce GTX 355.69 drivers. The GeForce GTX 355.69 drivers are not compatible with the GeForce GTX 960 for some reason.
We’ve reached out to NVIDIA to ask why the GeForce GTX 950 would have more memory bandwidth than the GeForce GTX 960 when it has slower clocked memory and features the same GM206 GPU albeit some things are disabled.