SwapBuffers bad performence
I have test application that periodicaly rendering scene when new data arive. Scene contains one quad with one texture no lights, no shaders. In each render i update texture with glTexSubImage2D (512B) one line of scene and call swapbuffers but call takes long time. "Long time" means longer time on Windodw7 laptop than on Windows XP laptop - i developed application on this pc.
PC WIN_7: Core i7, NVIDIA NVS 5500M, SwapBuffers takes 20ms
GL_VENDOR: NVIDIA Corporation
PC WIN_XP: DualCore, ATI MOBILITY RADEON 38500
SwapBuffers takes 5ms
Where can be problem? Why is SwapBuffers has so bad performence on better pc? Is it problem in WIN7/WINXP on NVIDIA/ATI?
Is there any general recommendation to discover this discrepancy?