AMD HD 6870, 6850 unshackled

Now that the NDA manacles have been removed, we can tell you what the fuss is all about. Today AMD finally lifted the veil on the new 6800-series GPUs and presented its Radeon HD 6870 and Radeon HD 6850 to the general public.

The two cards, built around the new Barts XT and Barts Pro chips are AMD's second generation DX11 architecture and introduce some new features and architectural improvements.

The reference specs for the Radeon HD 6870 and HD 6850 are as follows.

AMD has been fiddling with the Cypress core, and while it may call it a new architecture, it is in fact a Cypress-derived GPU.

As you can see, AMD has kept a pretty tight lid on things, with early divination pointing towards lower core clock speeds. This most likely has to do with AMD's marketing decision to place a mid-range GPU in a higher-ranked series. Up the clocks a bit, squeeze out an above-the-norm card and match it to the 6800-series family.

The HD 6870 sports just 1120 streaming processors (SPs), compared to the HD 5870s 1600. Its smaller brother, the HD 6850, sports 960 SPs, also short on the 1440 carried by the HD 5850. As you can imagine, these are not same-class GPUs, despite the naming. But you'd be fooled to think that based solely on specs. The reality is a bit different, it now seems.

While we've been waiting for the next big thing, AMD has tweaked performance on its GPUs as much as it has introduced new features such as UVD 3.0 and AMD HD3D (the equivalent to Nvidia's 3D Vision), as well as improving tessellation and some AA features. The introduction of DisplayPort 1.2 also allows you to perform Eyefinity6-equivalent display setups without so much hardware real-estate. Uncompressed 7.1 channel audio is now possible through the HDMI 1.4a, meaning high-quality lossless audio.

UVD 3.0 will support concurrent 1080p streams while also bringing with it colour and contrast enhancements that are supposed to make your movie-viewing experience that much more vivid. It also supports Blu-ray 3D.
So what about performance?

Many considered it strange that AMD, in a rather out-of-character way, was shuffling mid-range parts up the pecking order. Now, after we've looked at some benchmark results you can understand why AMD actually did this. The performance on the HD 6870, while not on par with its 5800-series counterpart, is much more efficient SP-for-SP. For 70 per cent of the SPs, you get 90 per cent of the performance. For reference, consider the HD 6870 like a HD 5850, and the HD 6850 like a HD 5830, in terms of raw performance.

Stream-processor-for-stream-processor AMD has done a bang up job by increasing efficiency while keeping costs down. The HD 6870 falls slightly short of the 5870 in raw performance, but you'll forgive AMD for that, considering it contains 30% less streaming processors than its 'predecessor' and costs £100 less.

You also get the power consumption of a HD 5850 instead of the greedy HD 5870. The chips are also smaller and therefore easier to yield defect-free parts, which also mean AMD has no need to put a huge premium on the cards... Which is exactly what it's done. For about £200 you can get an HD 6870, while the HD 6850 will run you about £150.

You might not like the marketing sleight of hand, but so far we're impressed with where this is going.

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