Windows 7, GUIminer, ASUS Crosshair IV Extreme Motherboard, 850 watt PS, Three XFX HD6870 video cards each at an average 280 MH/s= 840 total MH/s. I feel I could get over 300 MH/s from each and lower the power consumption if only MSI Afterburner would ACTUALLY underclock the memory. Have UOC enabled and memory set at 324 MHz, but it stays at 1050 MHz...

Two other rigs running also, one with two 5770's, and another with one 5770. They are getting 202 MH/s each and the memory is underclocked with MSI Afterburner and working correctly.

Total hashrate with all three systems is 1440 MH/s. Mining on 50BTC pool.