ATI radeon HD 4850

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.

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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.

Asus and Powercolor were the first board partners to get cards to us for review. Powercolor’s card is running stock clocks while Asus’ is from its T.O.P. range, which means it comes overclocked to 680MHz(core) and 2,100MHz(memory) straight out of the box. This understandably means the Asus card will cost a little more but the choice is there if you want a tad more performance.

Both cards come with the exact same bundle that includes converters for DVI-to-HDMI, DVI-to-VGA, S-video to composite, and S-video to component as well as a CrossfireX connector. Neither include any free games or other software but considering the approximately £120 asking price this is hardly surprising.

As a result of the cut down clock and memory speeds the cards consume less power and consequently kick out less heat than HD 4870. This means ATI has been able to use a single slot cooler for its reference design, which both cards we’re looking at today have utilised.

While this seems to make sense, ATI obviously never tried to swap out one of these cards after an extended gaming session because, my god, they get hot! Even ATI’s own Overdrive software reports that the cards are running at 80 degrees Celsius and above. Not that we experienced any stability problems, at least with Powercolor’s card. However, the Asus card, which was fine for most of our testing, didn’t fare so well. During Race Driver: GRID testing the card would regularly crash out and we eventually had to abandon testing with the Asus card. I asked an Asus representative about this and he informed us that indeed the reference cooler isn’t sufficient for reliable performance when the card is overclocked so retail versions of the T.O.P. card will use Asus’ Glaciator cooler instead.

An Asus nVidia 9600GT card utilising the Glaciator cooler
Now we’ve not seen a card with this cooler before so we can’t vouch for its abilities. However, from what we were told it enables the card to run nearly 20 degrees Celsius cooler than the reference design and, from reading around, the general opinion appears to be that this is also a very quiet and efficient cooler. Of course the obvious problem is that it will make the card semi-dual-slot, i.e. it won’t take up two PCI brackets, so you can still install a USB or audio panel, but you won’t be able to fit another full-size card in alongside.

One additional power connector is required to get the card going and this is situated in the normal position on the back edge. Likewise the Crossfire connectors are up top where you’d expect and outputs are the standard two dual-link DVI and combined S-Video/Composite/Component sockets.


All our testing uses a variety of manual run throughs and automated timedemos but regardless of which test method is used we monitor all tests to ensure performance is consistent. Where there are spurious results or dips in performance we will note this. We also do multiple run throughs then take the average of these and report that figure to you. The test setup is as follows:

Common System Components

  • Intel Core 2 Quad QX9770
  • Asus P5E3
  • 2GB Corsair TWIN3X2048-1333C9 DDR3
  • 150GB Western Digital Raptor
  • Microsoft Windows Vista Home Premium 32-bit


  • ATI: Catalyst 8.4
  • nVidia GTX200 Series: Forceware 177.34
  • Other nVidia cards: Forceware 175.16

Cards Tested

  • ATI HD 4870
  • ATI HD 3870
  • nVidia GeForce GTX 280
  • nVidia GeForce GTX 260
  • nVidia GeForce 9800 GTX

Games Tested

  • Crysis
  • Race Driver: GRID
  • Enemy Territory: Quake Wars
  • Call of Duty 4
  • Counter-Strike: Source


While it hasn’t been a huge commercial success and its gameplay is far from revolutionary, the graphical fidelity of Crysis is still second to none and as such it’s still the ultimate test for a graphics card. With masses of dynamic foliage, rolling mountain ranges, bright blue seas, and big explosions, this game has all the eye-candy you could wish for and then some.

We test using the 32-bit version of the game patched to version 1.1 and running in DirectX 10 mode. We use a custom timedemo that’s taken from the first moments at the start of the game, wondering around the beach. Surprisingly, considering its claustrophobic setting and graphically rich environment, we find that any frame rate above 30fps is about sufficient to play this game.

All in-game settings are set to high for our test runs and we test with both 0xAA and 4xAA. Transparency anti-aliasing is also manually turned on through the driver, though this is obviously only enabled when normal AA is being used in-game.

That difference in memory bandwidth obviously has a significant impact on performance as the HD 4850 is markedly slower than the HD 4870. Oddly, though, the overclocking on Asus’ card doesn’t appear to make any significant difference in this title. As for the rest of the competition, the HD 4850 is fighting quite some battle and is currently losing to the nVidia 8800 GT.


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