Surprisingly I was able to get the system to boot with a reference clock of 229MHz, but no more. I booted into the OS and figured I would give the ECS eOC program a shot to fine tune even further. I was able to use the utility to squeeze a few more MHz out of the system and still pass the benchmarks and stability tests. The final stable OC I was able to achieve was 4060MHz, which is a big improvement over past ECS boards I have tested. I was quite happy with this number for the overclocked tests.