The GPU core runs at 1GHz, which is the highest frequency any Radeon card has been clocked at. The HD 7700 is clocked 18% higher than the HD 6770, while its GDDR5 memory is slightly faster at 1250MHz (5.0GHz DDR). Still, pairing that frequency with a minuscule 128-bit memory bus gives the HD 7770 72GB/s of theoretical bandwidth, which is actually slightly less than the HD 6770. The HD 7770 still only comes loaded with a 1GB frame buffer – the same as previous-gen mid-range cards. We don’t doubt that board partners will release 2GB versions, but because HD 7770 isn’t designed for extreme resolutions, 2GB models aren’t likely to provide a performance boost. The HD 7770’s core configuration also differs from the older HD 6770’s. The new card carries 640 SPUs, 40 TAUs and 16 ROPs. In comparison, that’s actually 20% less SPUs than the HD 6770, while the TAUs and ROPs remain the same. Cooling the “Cape Verde XT” GPU is a large circular aluminum heatsink paired with a 75mm fan that generates very little noise during standard operation and under stress. The HD 7770 operates at near silence because even under load it only draws 80 watts and as little as 3 watts at idle, courtesy of the ZeroCore Power technology. The heatsink and fan are enclosed in a custom housing that conceals the front side of the graphics card, this is the same design that the HD 6770 used. Nvidia also employed a similar design with its GTX 560 series. To feed the card enough power, AMD has included a single 6-pin PCI Express power connector – the same setup you’ll find on the HD 6770 and GTX 560, as well as numerous other mid-range graphics cards. Naturally, the HD 7770 supports Crossfire and so there are a pair of connectors for bridging two or more cards together. The only other connectors are on the I/O panel. Our AMD reference sample has a dual DL-DVI connector, a single HDMI 1.4a port and two Mini DisplayPort 1.2 sockets. All HD 7700 series cards support a max resolution of 2560x1600 on up to three monitors. With a multi-stream hub using the Mini DisplayPort 1.2 sockets, the HD 7770 can drive up to five screens.
