AMD Radeon HD6870 review

Product AMD Radeon HD6870
Website www.amd.com/us/products/Pages/graphics.aspx
System Specifications 900MHz core, 1GB GDDR5 memory, PCI Express x16 interface, Eyefinity support, Crossfire-capable, double-slot form factor
Price £200 not including VAT

A WEEK AGO AMD unveiled the first member of its 'Northern Islands' GPU family (that's right, not the 'Southern Islands', which is the next generation for next year). Officially known as the AMD Radeon HD6870, this is the first Radeon part without any mention of ATI in the name. It brings improved multi-screen Eyefinity, Blu-ray 3D and stereo 3D support, along with somewhat lower power consumption. The increased number of shaders, improved DX11 tesselation and more efficient power usage - all despite keeping the same 40nm TSMC process - did bring an incremental performance jump here. Even with just over 1,100 shaders, the HD6870 came sufficiently close in benchmark results to the existing crown holder, the HD5870, that the name change from HD6770 seems to be justified.

After all, the shaders run faster at 900MHz versus 850MHz, and the efficiency is improved too. The 1,120 stream processors are joined by 56 texture units, 128 Z/stencil raster-ops (ROP) units and 32 color ROP units. Looking at single precision floating-point performance though, the shader number and clock speed are all that count. The 1,120 shader units at 900MHz in the HD6870 give exactly 2 teraflops peak, compared to 2.7 single-precision teraflops on the HD5870. Also, this being the upper end of the consumer segment and not the top-level prosumer class like the HD5870, the new card doesn't support double precision floating-point at all. The HD6970 and higher 'Cayman' parts will take care of that, with substantial performance improvements expected over the prior generation.

The 1GB of RAM sits on the same 256-bit bus as in the HD5800 series, with twice the bus width of the HD5770. This upgrade was necessary to match the Nvidia Geforce GTX460, the direct competitor targeted by this GPU. The HD6870 memory is rated as 4.2GHz GDDR5, higher than any overclocked versions of the GTX460 right now. But it's not something that Nvidia couldn't fix on an updated GF104 chip stepping, together with enabling all 384 shaders.

So, how does the HD6870 stack up against the GTX460? We already know that the general GTX460 1GB is beaten by the HD6870 1GB in most benchmarks, as seen by many review sites. However, what if we give Nvidia an unfair advantage and benchmark the cream of the crop GTX460 against the current plain vanilla HD6870, before the faster overclocked versions of the AMD card appear in November?

So, here we took one of the best GTX460 cards around, the Gainward GTX460 GS GLH "Golden Sample Goes Like Hell", which we reviewed a few months ago here. With an 800MHz GPU and 1GB of GDDR-4000 memory, it should be able to stage quite a fight for the AMD newcomer since, after all, this Gainward offering is easily a fifth faster than the standard GTX460 1GB offering.

Well, the GTX460 does gain an advantage in terms of size right away, being a third shorter, as you can see here:

I used both graphics cards in the same reference system: an Asus Maximus III Gene P55 board with X3470, a Xeon version Intel Core i7-870 processor and 4GB of Kingston HyperX memory running at DDR3-1333 CL6 speed settings. The usual newest drivers under Windows 7 64-bit edition with most pre-SP1 updates were also applied.

Here are the 3DMark Vantage results for the HD6870:

... versus the GTX460:

... and Unigine Heaven 2 results on the standard HD6870:

On the Gainward GTX460 GS GLH, the same Heaven run resulted in 36.8 FPS and an overall score of 926, which just about gives it the edge. As you can see, though, the HD6870's performance is not bad at all when looking at this quick run of the two popular benchmark tests. Physx helps the Gainward GTX460 GS GLH win the overall scores in the 3DMark.

If you exclude the Physx-accelerated CPU tests in 3DMark Vantage, and just look at the GPU tests in that benchmark, the HD6870 still manages to, in principle, have an advantage over even the best GTX460 card around. However, the advantage isn't big enough to completely outclass the Gainward-enhanced Nvidia offering, and, in Heaven 2 bench, the Nvidia part overclocked by Gainward was still a little faster.

I did notice that the Radeon ran noticeably cooler, whether in idle mode or during the benchmark run, compared to its competitor. And as I said, all Nvidia needs to do - if it wants, or can, of course - is to enable all the shaders on the GF104 die, and possibly speed up the memory a bit, and it should still be in the game. However, the power and heat issues might limit the performance enhancement - it's not just about the TSMC die yields.

On the other hand, based on overclockers' feedback, the HD6870 itself has a plenty of overclocking potential, so cards running at 950MHz or even 1000MHz and with correspondingly sped up memory should be out there within a month or two. The results could be turned the other way around then.

In summary - sadness for the loss of ATI brand aside - the AMD Radeon HD6870 is quite a good part that performed admirably even when faced with a handicap match with the top overclocked Nvidia GTX460 from Gainward. Kudos have to go to Gainward for offering such a fast GTX460. However, this won't mean much for Nvidia once more customised, overclocked HD6870 cards appear on the shelves in a few weeks.

In Short
This new AMD HD6870 graphics card clearly has near top-end performance at an almost mainstream price. While I'd have rather called it HD6860 to avoid the competitive confusion, it still justifies its positioning at just below the high end. In the second installment of reviewing the HD6870, we'll look at its Crossfire performance as well as its performance against the HD5800 series. µ

The Good
Decent performance for the £200 class price, DX11 enhancements, new features, cool and low power draw at 150W top power.

The Bad
Can't quite beat selected GTX460 overclocked parts, should have been named HD6860 as it's not faster than HD5870.

The Ugly
The prospects of HD5870 secondhand card sellers, and 3DMark benchmark CPU Physx fix is sorely needed.

Bartender's Score
9/10