I want to test on Windows 7 if my old ATI Radeon X1650 card can do better at rendering Direct3D 9 or OpenGL 2.
Does anyone know any software that can help with determining this, like a benchmark?
Here are 2 tools that allow you to test and compare both Direct 3D and OpenGL:
FogCity measures the Direct3D and OpenGL speed. (quite old, but it still works with Windows 7, free & portable)
Fraps is a universal Windows application that can be used with games using DirectX or OpenGL graphic technology. In its current form Fraps performs many tasks and can best be described as:
Games and most benchmark programs will not work, it is like comparing the acceleration of two different cars under two different sets of circumstances.
Games for DirectX will use one set of features and if they have a port do OpenGL, it will probably have a few different textures / feature and run differently - again, comparing apples and pears! (or whatever the saying is!).
What I would recommend instead is programs that are actually designed for both - such as 3dStudio Max (You can download a demo), and try rendeing a simple scene on either and time it.
You should be able to compare D3D and OpenGl performance on the same card.
Find a tool that allows you to choose the rendering engine - Unigine Heaven for example - run it in each mode and compare the results.
You can download it from here