Embodiments described herein relate to improving throughput of a CPU and a GPU working in conjunction to render graphics. Time frames for executing CPU and GPU work units are synchronized with a refresh rate of a display. Pending CPU work is performed when a time frame starts (a vsync occurs). When a prior GPU work unit is still executing on the GPU, then a parallel mode is entered. In the parallel mode, some GPU work and some CPU work is performed concurrently. When the parallel mode is exited, for example when there is no CPU work to perform, the parallel mode may be exited.