1. In a graphics processing system, a method for selecting command threads for processing, the method comprising: selecting, by an arbiter circuit implemented by the graphics processing system, command threads from among a plurality of pixel command threads and a plurality of vertex command threads, wherein the arbiter circuit selects a pixel command thread as a selected command thread and a vertex command thread as another selected command thread; intermixing, in an order determined based on a command of the selected pixel command thread and a command of the selected vertex command thread, an execution, in an arithmetic logic unit, of commands of the selected pixel command thread with commands of the selected vertex command thread; maintaining a first status of the selected pixel command thread, wherein the first status is used by the arbiter circuit to perform the selecting of the selected pixel command thread; and maintaining, concurrently with the first status, a second status of the selected vertex command thread, wherein the second status is used by the arbiter circuit to perform the selecting of the selected vertex command thread.