I cannot do anything but guess. I recommend that you stay with the 8-8-8-24, or the 9-9-9-24 (which ever you currently have). The problem is not the speed of the RAM (which mobos can arbitrate) but the latency. If you were mixing DDR 1333 and DDR 1600 with the same latency I would predict that it would work as DDR 1333. But matching the latency is another problem. I have not seen any reports of people mixing latencies and having a successful result.