I have a propietary media player that runs on Windows 8 in desktop mode. Runtime DirectX version is 11, but native graphics driver support is for DirectX 9.
On some computers with the exact same setup, I see that the actual swap chain's back buffers count is 2, and the performance is great, and on some others the back buffer count is 7 and there are frames dropped.
I don't have the source code of that player and wonder what could be the reason for determining the different back buffer count number in runtime.
Can someone please explain why such backbuffer count leads to such change in performance? Or just point me to relevant documentation that explains the implications of backbuffers number?
(More debugging info: Using GPUView I see that when backbuffer count is 2 the hardware works in a synchronized mode, i.e. one packet in the HW queue in each second VSync (Clip frame rate is 30fps), when for the 7 backbuffers the work is done for 5-7 frames together, then some empty VSyncs, then 5-7 frames again and so on).
Thank you in advance!
Well, I got an answer from Microsoft. This is in order to save power when working on DC (battery) - that way the processor can be awake for processing all available buffers, send them to GPU to work on and move to a deeper power saving mode for a longer time.