This is a 50MHz overclock for both the GPU and memory, and Asus is currently the only partner that has an overclocked card, at least as far as we know. Another interesting thing is that Asus included its Voltage Tweak Technology with the Asus EAH4770 TOP card which raises the GPU voltage from 0.95V to 1.2V. This voltage boost is enough to raise GPU and memory frequencies from 800MHz to 971MHz and from 3400MHz to 4600MHz.
Source: FUD Zilla