- developer: Fraps
Fraps is designed as a generic tool to monitor framerates in DirectX games. The name itself is derived from the term Frames Per Second (FPS) which is what the program displays in the corner of the game's screen. It measures the framerate by monitoring calls to the Flip procedure in DirectDraw. The game calls the Flip function when it is using double buffering and needs to switch between the two surfaces. As an entire screenful of data is transferred from the buffer, the Flip function waits for the vertical retrace of your monitor before writing the new data to the screen. By waiting for the retrace (when there is no activity on the monitor), the game avoids writing data as it is being shown which causes flickering. This also gives us the opportunity to keep track of the number of frames actually drawn over any time period.
Fraps will not work with games that do not use buffering (and the Flip function). Games that do not use buffering are generally ones that do not write large amounts of data to the screen. Typically this will involve games that have static backgrounds and move sprites around (such as War and Realtime Strategy games). Due to the small amount of data being transferred to the screen by these games, they will typically run at your refresh rate anyway, so don't be too concerned. What you should be worried about are the rates in games using complex 3D environments, and this is what Fraps works best with.