http://www.amd.com/us/products/desktop/graphics/7000/7770/pages/radeon-7770.aspx#2 for reference. Look at the Specifications tab and you will find the following.
"AMD Eyefinity multi-display technology1
Up to 6 displays supported
Independent resolutions, refresh rates, color controls, and video overlays
Display grouping
Combine multiple displays to behave like a single large display
Discrete Digital Multi-Point Audio (DDMA)"
AMD Eyefinity technology works with games that support non-standard aspect ratios, which is required for panning across multiple displays. To enable more than two displays, additional panels with native DisplayPort™ connectors, and/or DisplayPort™ compliant active adapters to convert your monitor’s native input to your cards DisplayPort™ or Mini-DisplayPort™ connector(s), are required. Support for six simultaneous displays may require complementary products compatible with DisplayPort 1.2 Multi-Stream Transport. Maximum number of configured displays may vary - check with your component or system manufacturer for specific model capabilities and supported technologies. SLS (“Single Large Surface”) functionality requires an identical display resolution on all configured displays.
Most current cards with Eyefinity capability have at least a maximum of 4 monitors if not 6.
Up to 6 displays
AMD Radeon™ HD 7900 Series
AMD Radeon™ HD 7800 Series
AMD Radeon™ HD 7700 Series
AMD Radeon™ HD 6900 Series
AMD Radeon™ HD 6900M Series
AMD Radeon™ HD 6800 Series
AMD Radeon™ HD 6800M Series
AMD Radeon™ HD 6700M Series
AMD Radeon™ HD 6600M Series
AMD Radeon™ HD 6500M Series
ATI Radeon™ HD 5800 Series
Up to 5 displays
AMD Radeon™ HD 6700 Series
ATI Radeon™ HD 5700 Series
Up to 4 displays
AMD Radeon™ HD 6600 Series
AMD Radeon™ HD 6500 Series
AMD Radeon™ HD 6400M Series
AMD Radeon™ HD 6300M Series
Up to 3 displays
AMD Radeon™ HD 6400 Series
ATI Radeon™ HD 5600 Series
ATI Radeon™ HD 5500 Series
ATI Radeon™ HD 5400 Series