DX7:
device.Clear 1,vp_rect,D3DCLEAR_TARGET,clscolor,0,0
OpenGL:
glClear GL_COLOR_BUFFER_BIT
This is obviously a GPU/Driver related phenomenon if DrawRect() is faster or slower compared to Cls(). This really isn't going to change your fps in a real world scenario, especially if you're already drawing a bunch of objects. But, in a situation where every cycle counts, you may want to add a "performance test" section to your game options and auto configure your render loop based on the results.
device.Clear 1,vp_rect,D3DCLEAR_TARGET,clscolor,0,0
OpenGL:
glClear GL_COLOR_BUFFER_BIT
This is obviously a GPU/Driver related phenomenon if DrawRect() is faster or slower compared to Cls(). This really isn't going to change your fps in a real world scenario, especially if you're already drawing a bunch of objects. But, in a situation where every cycle counts, you may want to add a "performance test" section to your game options and auto configure your render loop based on the results.