If you care about efficiency, then you are burning significantly more energy to run at 4GHz, and are still moving the same amount of data in and out of your loc

If you care about efficiency, then you are burning significantly more energy to run at 4GHz, and are still moving the same amount of data in and out of your local memory. If that is your bottleneck, then you are running at 4x the clock speed for no real gain, as your memory can't keep up with the speed of your functional units. But to answer your question directly, we are targeting 1GHz conservatively...we think it could do more, but as we are focused on efficiency, we think it is a good middle ground between performance and energy usage. We'll be able to make a more informed decision (and possibly change that) when we have silicon in hand.