Originally posted by: lopri
GDDR5 is what makes RV770 really fly, from what it looks like. I mean, the only difference between HD 4870 and HD 4850 is the memory (and yes, some core overclocking).
Here's an article (in French, but the graphs need no translation) which examines the performance effect of different memory speeds in the 4800 series cards:
http://www.hardware.fr/article...-4800-gddr5-utile.html
A few conclusions can be drawn upon examining the results:
* The average performance delta between the 4850 and 4870 increases with AA enabled
* At 1920x1200 the 4870 is about 25% faster than the 4850
* With both gpu's clocked at 725MHz the gddr5 version is 8-12% faster
* With 725 core and 993 mem clocks for both cards the gddr5 version is actually 10-12% slower (which doesn't really say much because I'm sure the 4870 gpu and the driver are tuned for 1800MHz memory clocks, so it's about as relevant as to putting high octane gas into a low tech engine and claiming it provides no benefit)