Asus Radeon HD 7870 DirectCU II full review

We've already seen entrants from Asus' new 7900 and 7700 series (codenamed Tahiti and Cape Verde respectively). But this particular AMD Radeon HD 7879 graphics card comes from the series midway point between those two, the 7800 ‘Pitcairn' range.

For those who adore high frame-rates and so want something with more grunt than the more mainstream 7700, but yet can't (or don't want to) go as high as the eye-watering 7900, a card like the Asus Radeon HD 7870 DirectCU II makes an awful lot of sense. The question is whether it's worth paying that little bit more for something like the nVidia GeForce GTX 670.

Is the Asus Radeon HD 7870 DirectCU II a slimmed-down 7970 or a pumped-up 7770? Well, the 7870 (now manufactured using the 28nm process) has many similarities with a cut-down 7970, but it isn't afraid to adopt a different tack where needed. It features 2GB of GDDR5 RAM rather than the 7970's 3GB, a figure that shouldn't have too much of an impact on today's gaming. The Asus Radeon HD 7870 DirectCU II's standard 1200MHz memory clock has, in this Asus edition, been raised slightly to 1210MHz. See alsoGroup test: What's the best graphics card?

With the quadrupling effect of the GDDR5 memory, that results in an effective figure of 4840MHz, which is more some way down on the HIS 7970's figure of 5500MHz. The Asus Radeon HD 7870 DirectCU II's memory interface has also been marked down from 384-bit to just 256-bit, and the 7870's memory bandwidth of 154.9GBps is a long way adrift of the 7970's 264GBps – while itself remaining a considerable improvement on the Club 3D 7750's figure of 72GBps.

The core clock, surprisingly, is higher though, and the Asus 7870's figure of 1010MHz (slightly up on the default setting of 1000MHz) is a very great improvement on the 925MHz core-clock speed of the HIS Radeon HD 7970. That means that the 7870's pixel fill-rate of 32.3GPps is actually higher than the 7970's 29.6GPps.

Overall graphics speed will be much reduced in the case of the Asus Radeon HD 7870 DirectCU II though. While the number of ROPs (Raster Operation Pipelines) are unchanged from the 7970, there are fewer texture units (80, down from 128), and the texture fill rate of 80.8GTps is significantly down on the 7970's figure of 118.4GTps. This figure is also somewhat down on the 102.5GTps notched up by the slightly more expensive GeForce GTX 670.

The number of stream processors has been cut from 2048 to a less stellar 1280. It is worth noting, however, that the high-end card from the previous generation only had 1536 stream processors, and this remains a relatively competitive figure for the price. The nVidia GTX 670 offers 64 more stream processors, but costs an extra £50.

The Asus Radeon HD 7870 DirectCU II is fairly light on power. While the 7970 hit figures in excess of 225 watt, the 7870 checks in at a far more modest 175 watt. This places it just five watt ahead of the GTX 670. In testing the difference was a little wider than that, with an average difference of around 12-14 watts.

The nVidia cards remain the best for power consumption, although the Asus Radeon HD 7870 DirectCU II isn't as far behind the nVidia GTX 670 as we might have expected.

As with its higher-end brethren, the Asus Radeon HD 7870 DirectCU II follows the AMD's new Graphics Core Next architecture. That means extra versatility, with the new-look Compute Units able to work on instructions individually rather than relying on related sets of instructions being bundled together for top performance.

However, while this makes the new AMDs better suited to a gaming world in which graphics cards are often expected to deal with a hugely varied mishmash of instructions at any one time, it hasn't yet made for devastating increases in real-world gaming frame-rates. And since the 7870 has just 20 Compute Units, rather than the 32 of the 7970, the results are correspondingly even less impressive here.

Asus Radeon HD 7870 DirectCU II: Performance

In terms of benchmarks, the Asus Radeon HD 7870 DirectCU II is very much put in its place by the GTX 670, despite that card only costing around £50 more.

While the GTX 670 is very competitive against the 7970, the 7870 lags some way behind.

In BattleForge, for example, while the GTX 670 and the 7970 are fighting it out on figures of 79 and 80fps, the 7870 is stuck down at 71.3 at a resolution of 1680 x 1050.

At the higher resolutions of 1920 x 1200 and 2560 x 1600, its figures fall to 59.4 and 41.2fps, while the GTX 670 remains at 66.8 and 45.9fps.

In Crysis, the 7870's figures of 42.6, 33.7 and 22.6fps across the three resolutions fail to stack up against the GTX 670's 47.9, 39.4 and 25.8fps.

In Stalker, the figures of 79.2, 71.3 and 49.5fps are again very much inferior to the GTX 670's.

Asus Radeon HD 7870 DirectCU II: Benchmarks:

Crysis 2 (1,680x1,050 / 1,900x1,200 / 2560x1600)                42.6 / 33.7 / 22.6
Battleforge (1,680x1,050 / 1,920x1,200 / 2560x1600)                71.3 / 59.4 / 41.2
Stalker Pripyat (1,680x1,050 / 1,920x1,200 / 2560x1600)            79.2 / 71.3 / 49.5


Asus Radeon HD 7870 DirectCU II: Specs

  • AMD Radeon HD 7870
  • 2GB GDDR5
  • 1010MHz core clock
  • 1210MHz memory clock (4840MHz DDR effective)
  • 400MHz RAMDAC
  • 256-bit memory interface
  • 1280 stream processors
  • 80 texture units
  • 32 ROP units
  • 20 Compute Units
  • PCI-E interface
  • 2 x 6-pin power connectors
  • DirectX 11.1
  • 1 x DVI, 1 x HDMI, 2 x Mini-DP
  • 2-year warranty