How to read GPU (graphic card) temperature?

windows api driver temperature video-card

For nVidia you would use nvcpl.dll.

Here's the documentation:
http://developer.download.nvidia.com/SDK/9.5/Samples/DEMOS/common/src/NvCpl/docs/NVControlPanel_API.pdf

windows api driver temperature video-card

I found this: AMD Display Library SDK (ADL for short). That covers ATI cards.

http://developer.amd.com/display-library-adl-sdk/

Link to the original page, via Wayback Machine:

http://web.archive.org/web/20101103020811/http://developer.amd.com/gpu/adlsdk/Pages/default.aspx