The Most Comprehensive AMD Radeon Linux Graphics Comparison
Radeon HD 4670: The Radeon HD 4670 has the RV730XT core at 750MHz while the 512MB GDDR4 video memory is clocked at 1100MHz by default.
Radeon HD 4770: The Radeon HD 4770 is an RV740 with an engine clock of 750MHz and memory clock of 800MHz for its GDDR5 video memory.