You may have gathered over the last couple of weeks that we really like the ATI HD 4870. It isn't quite the fastest graphics card you can buy - that honour goes to nVidia's GTX 280 - but it performs very well and comes in at a quite phenomenal price. Still, there are many of us that would balk at the idea of spending nearly £200 on a graphics card, regardless of how fast it is, which is where the ATI HD 4850 comes in.
Like its more expensive sibling, the ATI HD 4850 is based on ATI's new RV770 chip. In fact, unlike the nVidia GTX 260, which uses the same chip as the GTX 280 but with a few sections disabled, the HD 4850 uses the full extent of RV770. The differences are confined to clock speed and memory configuration.
So, in essence you still get 800 stream processors, 40 texture address/ filtering units, and 16 ROPs, as well as the 256-bit wide memory interface - although the memory chips themselves are GDDR3 instead of the GDDR5 seen on the HD 4870. However, the core clock speed has been reduced by 17 per cent and memory speed by 45 per cent, which should result in a performance differential that sits somewhere within that percentage range - exactly what the difference will be will differ from game to game.
And that really is it. There's nothing more to say about the architecture of HD 4850 that hasn't already been said in our in-depth HD 4870 review. However, when it comes to the card itself there are some significant differences.