I don't know very much about this, but do you think that part of your success has just been the benefit you get from going from dynamic ram to static ram? Seems that alone would give you a baseline performance improvement?
GPUs use dynamic RAM too (though discrete cards usually have GDDR rather than DDR, which gives higher bandwidth). The most fundamental difference between a CPU and GPU isn't the memory hierarchy (modern GPUs are growing cache hierarchies as well) but the core architecture (vector/highly threaded "small cores", vs. out-of-order/superscalar "big cores").
