1. In a graphics processing system, a method for selecting a command thread for processing, the method comprising: providing, by an input arbiter implemented by the graphics processing system, a plurality of pixel and vertex command threads to each of a first and second reservation station; selecting, by an arbiter implemented by the graphics processing system, a pixel command thread from the plurality of pixel command threads; selecting, by the arbiter, a vertex command thread from the plurality of vertex command threads; selecting, by the arbiter as the command thread, either of the pixel command thread and the vertex command thread; maintaining a state of a selected pixel command thread or vertex command thread; providing, by the arbiter, the command thread to a first command processing engine operatively connected to the arbiter; and providing, by the arbiter, either of the pixel command thread and the vertex command thread that was not selected as the command thread to a second command processing engine operatively connected to the arbiter.