ATI HD4870 and HD4850 GPU Overclock Performance Scaling

Google translated article, with lots of charts showing overclocking scaling of the HD4000 GPU. They tested GPU speeds between 600~800Mhz and Memory speed 2000~4000Mhz

Since leaving 4800 series graphics cards companies AMD, users received two excellent graphics card for moderate money: Radeon 4850 and Radeon 4870. Both maps are based on videochipa RV770 and technologically, they are no different, except for a different type of memory:
-- From the Radeon 4850 it DDR3 operating at a frequency of 2000 MHz;
-- From the Radeon 4870 it DDR5 operating at a frequency of 3600 megahertz.
Many users interested in the question: what gives videochipu RV770 DDR5 memory? Also interesting: is it possible to disperse the younger Radeon 4850 graphics card to the level of performance, senior Radeon 4870?