8 Pack from Overclockers UK performed a pretty impressive overclocking feat by clocking two AMD Radeon R7 240 graphics cards in CrossFire from 720MHz to 1590MHz - an overclock of 120 percent! The feat was achieved with LN2 cooling and three $99 EVGA E-power boards per card; one each fore Core, PII and Vmem. He also needed three 1200W PSUs for the needed PCIe power connectors.
How high did he get the cards? He got the Radeon R7 240?s core clock from 720MHz all the way up to 1590MHz! He used 1.4v and chilled them down to -45C. That was good enough for a 3DMark 11 score of P8957. That is pretty wicked, but he also went over the top to get that score.