ATI Radeon 4870 and 4850 Hands-On Preview

By: James Yu Posted on June 24, 2008

The GPU game is changing. In the past, each graphics-generation launch started with the release of a massive new flagship GPU to take over as the top card in the product lineup. Nvidia opened the latest video-card generation by launching its flagship $649 GeForce GTX 280 and $399 GTX 260 GPUs last week. Big GPU launches generate a lot of excitement, but not many people have the budget for a $500-$600+ video card. That's why the graphics manufacturers work furiously to ship out new GPUs targeted toward the more affordable price points after the big tech launch. Nvidia's mainstream GTX 200 GPUs may be a few months away, but ATI is ready today with its Radeon HD 4870 and HD 4850 GPUs, thanks to a new shift in GPU design strategy.

ATI, AMD's graphics division, used to follow the same "big chip first, smaller chips later" launch plan, but the ballooning transistor counts and growing silicon die sizes of these GPUs encouraged the company to change its design philosophy. The problem with large chips is that they're more expensive to produce than small chips. You get fewer chips from each silicon wafer, and the greater surface area per chip also increases the chances of having a defect that will force the manufacturer to either disable parts of the chip and sell the GPU as a lower-quality model or discard the entire chip if the defect occurs in a particularly critical location.

ATI's solution to the large-GPU problem was to design a reasonably sized GPU for the mainstream and enthusiast markets, and then bundle up two of those chips to create a product for the high end. ATI tried out the strategy starting with its Radeon HD 2900 and 3800 series cards, with mixed success. The Radeon HD 3870 was ATI's top single-chip GPU, and it compared best with Nvidia's midrange GeForce 8800 GT in the $200 price range. ATI put two of those GPUs on a single board to create the Radeon HD 3870 X2 to go up against Nvidia's GeForce 8800 GTX. The ATI Radeon HD 3800 series of cards offered good 3D performance and outstanding features such as full high-definition multimedia interface output with integrated audio, but they could never quite overcome their Nvidia counterparts in the game benchmarks.

ATI is confident that the performance rankings will be different with its Radeon HD 4800 series, at least for cards within price range of the Radeon HD 4870 and the Radeon HD 4850. At $299, the Radeon HD 4870 matches up best against the GeForce 9800 GTX, and the Radeon HD 4850's $199 MSRP puts it right up against the GeForce 8800 GT. ATI is preparing a dual-GPU Radeon HD 4870 X2 to go up against Nvidia's GTX 200 series cards this August.

GPU	Radeon HD 4870	Radeon HD 4850	Radeon HD 3870 X2	Radeon HD 3870
Current price	$299	$199	$399	$169
Stream processors	800	800	320x2	320
Core clock	750 MHz	625 MHz	825 MHz	775 MHz
Memory	512 MB	512 MB	512 MB x2	512 MB
Memory clock	3.6 GHz GDDR5	2.0 GHz GDDR3	1.8 GHz GDDR3	2.25 GHz GDDR4
Memory Interface	256-bit	256-bit	256-bit	256-bit

The 800 stream-processor count immediately jumps out at you when you first see the specifications for the Radeon HD 4870 and the 4850. That's more than double the 320 on the Radeon HD 3870. Both of the Radeon HD 4800 cards have 800 stream processors, but the 4870 has a higher 750 MHz engine clock and comes with advanced GDDR5 memory. Graphics companies have been burned in the past by trying to build a new GPU release around unproven technologies (for example, by trying to jump to a smaller manufacturing process), but it looks like ATI was able to work out GDDR5 just in time for the 4870. GDDR5 offers much higher bandwidth than GDDR3 while drawing less power. The Radeon HD 4870 has 512 MB of 3.6GHz GDDR5 compared to the 4850's 512MB of 2.0GHz GDDR3.

The Radeon HD 4800 cards, like the last-generation Radeons, support DirectX 10.1. Game developers have been slow to adopt DirectX 10.1--which may be due to the fact that Nvidia GPUs, including the new GeForce GTX 200 series, don't have DX 10.1 support yet--but there are a couple of games on the horizon that will incorporate it, including BattleForge, a real-time strategy game from EA's Phenomic Studio, as well as an unannounced game from Sega that we will likely learn more about next month at E3 2008.

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You'll need a motherboard with an open PCI Express x16 graphics slot and a moderate power-supply unit if you want to upgrade to the Radeon HD 4870. Our MSI Radeon HD 4870 card has a dual-slot design and two 6-pin power connectors. The card is very energy efficient and draws only 160 watts at full power, which means that you need only a 500W power supply for single-card operation or 600W for two cards running in CrossFire mode. Both cards are also able to operate in three- and four-way CrossFireX mode provided that you have a CrossFireX-enabled motherboard, the appropriate number of open PCI Express slots, and enough power to keep them happy.

The new GPUs can also dynamically adjust power usage based on application demands. The GPU might power down for basic Web browsing, but it can respond immediately once you launch Crysis.

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The Radeon HD 4850 is slightly less powerful than the 4870, but that also means that it has more reasonable system requirements. The 4850 is a single-slot card with just one 6-pin power connector. Our Sapphire Radeon HD 4850 comes with a 450W power-supply recommendation for single-card operation and 550W for dual-card CrossFire.

Both cards feature two dual-link-capable DVI-I video-output connectors and a 7-pin video connector that can output S-Video as well as composite and component with an adapter cable. The Radeon HD 4800 GPUs also have integrated sound processing that lets each card output an HDMI stream with full HD video and 7.1 surround sound. The chips support HD video decoding for all of the major file formats (H.264, VC-1, and MPEG-2) as well as dual-stream, picture-in-picture playback. The new GPUs can also convert standard DVDs up to HD resolution.

We anticipate that most cards will ship with a DVI-to-HDMI adapter in addition to the standard DVI-to-VGA adapters, but we recommend reading the product description carefully just to make sure everything that you want is included in the box.

We put our MSI Radeon HD 4870 up against the GeForce 9800 GTX, the Radeon HD 3870 X2, and an overclocked EVGA e-GeForce 9800 GTX that matches the specs of Nvidia's new GeForce 9800 GTX+ for the single-GPU tests. The GTX+ has the same number of processing cores as the standard GTX, but comes with a 738 MHz core clock and 1.836 GHz processor clocks compared to the GTX's 675 MHz core and 1.69 GHz for the processors. According to Nvidia, the GeForce 9800 GTX+ will be available on July 16 for around $229, which should put it somewhere between the 4870 and the 4850. We broke out the GeForce 8800 GT and the single-GPU Radeon HD 3870 to go up against our Sapphire Radeon HD 4850. Then wedoubled up the cards and tossed in a GeForce GTX 280 for the dual-card CrossFire and SLI comparisons

System Setup: Intel Core 2 Extreme QX9775, Intel D5400XS, 4GB FB-DIMM (2x2GB), Windows Vista SP1, 750GB Seagate 7200.10 SATA Hard Disk Drive. Graphics Cards: GeForce GTX 280 1GB, EVGA e-GeForce 9800 GTX KO 512MB (Overclocked to GTX+ speeds), GeForce 9800 GTX 512MB, GeForce 8800 GT 512MB, Radeon HD 4870 512MB, Radeon HD 4850 512MB, Radeon HD 3870X2 1GB, Radeon HD 3870 512MB. Graphics Drivers: ATI Catalyst 8.6, beta ATI Catalyst series 5, Nvidia ForceWare beta 177.39, beta Nvidia Forceware 175.19.

The Radeon HD 4870 leads the pack in most of the single-GPU tests and shows decent scaling in CrossFire mode. The Radeon HD 4850 is a huge improvement over the Radeon HD 3870, but it looks like the GeForce 9800 GTX+ will be strong competition if Nvidia can keep prices below $229. The Call of Duty 4 performance is a concern, but we've found that map and demo selection can skew performance significantly in Call of Duty 4. We get rid of demos entirely in Call of Duty 4 and hand-drive our player through the Bog level while benchmarking on Fraps. We used the "Assault" demo for Crysis and a homemade demo for Team Fortress 2.

Nvidia isn't alone in advancing general processing on the GPU. ATI has also made progress with its own GPGPU initiative. As with Nvidia's CUDA, most of ATI's software support has been in specialized life science, financial, and oil and gas exploration applications, but there are consumer applications on the way. ATI has of course been accelerating Folding@Home for a couple of years now, but we'll soon see GPU-accelerated image-manipulation support from Adobe, and Cyberlink demonstrated GPU transcoding acceleration for its upcoming Power Director 7 application at a recent Radeon 4800 series media event in San Francisco. ATI has also partnered with Havok to work on supporting GPU physics acceleration in games.

It looks like we can slide the ATI Radeon HD 4870 right into the best card available slot at the $300 mark. Its closest competition might just be two GeForce 8800 GT or two Radeon HD 3870 cards paired up in their respective SLI or CrossFire modes. The Radeon HD 4850 also looks like a compelling choice at the $200 price point. It beats out the GeForce 8800 GT, but the GeForce 9800 GTX+ will be formidable competition when it comes out in July. Nevertheless the Radeon HD 4850 remains a great choice for price-conscious gamers looking for the latest in PC graphics at a reasonable price.