My Sapphire 290 is hashing at around 860kh/s. It is very important to have the correct configuration as many have said. Mine runs at 1000core and 1500mem. If I change it more than 5 either way the hashes go into the 600's or less. I haven't tweaked voltage yet, but am pretty content at this setting. Research the threads as some brands of 290's have better memory brand than others that do better with higher clocks. My sapphire is not one of those cards!