to see if the card is throttling back, make sure you have coolbits installed then go into the driver settings of the classic control panel and you will se a debug settings tab. look in there. it will have errors listed if the card is throttling back. mine was doing some silent throttling at 620mhz core. and higher than 620mhz on the core resulted in hard freezing for a minute while the clocks speeds dropped. at 615mhz on the core the card has given me no errors at all. and the memory is brilliant going to 865mhz. although coolbits limits me to 840mhz.