Modern CPUs provide many cores, which can run threads in parallel. It stands to hypothesize that this might be already enough to 100% render a game just on this cores, without the GPU involved. Develop a software based renderer that uses the VGJS system to parallelize render tasks.
If you are interested in this topic or for more information please contact Prof. Helmut Hlavacs (helmut.hlavacs(at)univie.ac.at).