Nvidia has been basking in the success of its Fermi-based GTX460 card lately, a Fermi card that finally offers something that most people want; namely provide a good bang for the buck. That’s something it does rather well, in fact, which can’t be said for most of its Fermi-based siblings. Not one to let its competitors bathe in any glory for too long, AMD has launched the HD6800 series of cards to deal with the threat. The first card we have seen using the new core is from Sapphire, with the HD6870.
Don’t let the name fool you, as AMD has been tinkering about with its naming policy, so the HD6870 is not as, you might think, a replacement for the previous generation HD5870. It’s more to do with offering matching performance but at a much lower cost, to counter the threat of the GTX460. As an example, the Sapphire HD5870 costs around £250, whereas the HD6870 can be had for around the £185 mark.
The new 40nm core carries the codename Barts: yes, that’s right, AMD is no longer using trees as codenames, having moved on to Caribbean islands (Cayman and Antilles are the next two higher end cores to come). The new core isn’t a major step forward like the HD5xxx series was from the previous one, being more about refining the core into a smaller die size and improving the performance per watt.
One thing that AMD has improved in the new core is the tessellation performance, something the HD5800 cards had a struggle with under load. By reducing the tessellation bottleneck by enhancing the tessellation buffering and improving the thread management in the shader engines, AMD has pulled much better performance out of the new core.
In that neat trick that only technology seems to be able to do, the Barts’ core has a smaller die size at 255mm² (as compared to 334mm² of the HD5850), has fewer transistors (1.7 billon compared to 2.15 billion), fewer Stream processors (1,120 compared to 1,440) yet still manages to outperform the HD5850. The reason behind the performance increase is better and more streamlined communication in the rendering pipeline and the faster clock speeds of the new core.
As you might expect for one of the first cards out on the market, Sapphire’s Radeon HD6870 follows the reference design with the exception of the sticker on the cooler. The core clock is the reference 900MHz while the 1GB GDDR5 runs through a 256-bit memory bus and is clocked at 1050MHz (4.2GHz effective) giving a memory bandwidth of 134.4GB/sec.
With a maximum power load of 151Watts the card makes do with just two 6-pin PCI-E power connectors on the top of the PCB in addition to what the PCI-E slot provides. The back plate holds plenty of connections: two Dual Link DVI and two mini DisplayPort 1.2 outputs and a single HDMI 1.4a port.
Performance-wise the HD6870 competes well against the GTX460. In FarCry 2′s built-in benchmark using the small ranch map at a 1280 by 1024 resolution with all the in-game details set to ‘ultra’, Sapphire’s HD6870 produces an average frame rate score of 92.56, while the Asus GTX460 Top gives 89.13fps. When the resolution is upped to 1920 by 1200 with the same in-game details but with 4x FSAA filtering added, the GTX460 just comes out on top with 65.21fps as compared to the HD6870′s 62.89fps.
Sapphire has also put together an impressive bundle with the card comprising DVI to VGA adaptor, a couple of 4-pin Molex to 6-pin PCI-E power connectors, Crossfire bridge and, very usefully, a full length HDMI cable and a mini DP to DisplayPort adaptor. Sapphire has also bundled in a copy of its brand new overclocking and tuning utility called Trixx.