Ati's Radeon HD 5970 (Codename: Hemlock) is going for DirectX 11 performance crown. PC Games Hardware tests if the two Cypress GPUs in Crossfire mode can fulfill this ambitions.
With the HD 5970 Ati continues the tradition to combine two graphics chips on a single card to deliver the fastest graphics card on the market and thus the highest number of frames per seconds for the gamers. PC Games Hardware tests the new Radeon against Nvidia's flagship, the Geforce GTX 295 as well as a SLI combo of two GTX 285s and of course the single-core sister model HD 5870. For this review we also added two new games to our benchmark selection Anno 1404: Dawn of Discovery and Call of Duty: Modern Warfare 2.
Radeon HD 5970 reviewed: Specifications
The "X2” tag is history: AMD's new dual GPU card gets a higher model number instead. Like all chips of the Evergreen family the Radeon HD 5970 supports DirectX 11. With two fully-fledged Cypress graphics processors like they are used on the HD 5870, the HD 5970 deals a lot faster with any calculation than the other cards of the HD 5000 series. But in order to meet requirements imposed by cooling and power consumption the chips are running at the frequencies of the HD 5850 only: 725/2,000 MHz (GPU/VRAM). In theory 1,600 Shader ALUs, 160 Texture Units and 64 ROPs are available. But since the Crossfire technology used does not scale to the full extend, the performance is not doubled.
The communication between the two chips on the board is controlled with a bridge chip from PLX. It is placed in the middle and is compatible to PCI Express 2.1. Thus the graphics chips have access to the full bandwidth. But this never - in contrast to the following - has been a real problem.
In the chart below we listed all the important specs.
Please note that the Asus Mars has only been listed exemplarily since the limited 1000 Euros card is out of stock by now. It would have been the only card that could threaten the Radeon HD 5970. Radeon HD 5970 reviewed: Micro Stuttering
Many had hope that the Radeon HD 5970 would not be affected by micro stuttering - the irregular output of frames to the display. This phenomenon is caused by the multi GPU rendering method AFR. With the Alternate Frame Rendering the graphics chips are taking turns in calculating full frames. Due to the different workload of individual frames it can happen, that several pictures are ready almost simultaneously, followed by a bigger time frame until the calculation of the next image is done. This results in frame distribution that feels like a lower framerate than actually is delivered. To put it bluntly: The felt framerate of the HD 5970 does not necessarily match with the real framerate.
The degree of the micro stuttering can be compared to the predecessor Radeon HD 4870 X2 and thus varies between acceptable (Crysis Warhead) and catastrophically irregular (Call of Duty: World at War and Modern Warfare 2).
Micro stuttering (aka Fake FPS in some forums) is recognized differently by every single person. Usually the problem gets noticeable with framerates below 40 fps and becomes obvious below 30 fps. Here the HD 5970 has a big advantage: Due to its huge calculation power it rarely drops to those frame levels if games are running in common settings. But since the graphically extraordinary Supersampling Anti Aliasing, which Ati advertises, lowers the frame rate below 30 fast, the problem comes into effect similarly fast. Radeon HD 5970 reviewed: Board and Cooling
With a length of 30.9 centimeters the Radeon HD 5970 is one of the longest graphics cards at all. Thus it places itself in line with devices like the Geforce 7900 GX2 or the Voodoo5 6000. The overall length is not caused by the board though, but by the plastic cover of the cooler. The PCB is "only” 29.3 centimeters long. For many common PC cases this length is complicated. If you are interested in the HD 5970, you should measure your case first and take the appropriate steps if necessary: Removing fans or hard drive cages might just give the required space.
Let's take a look at the naked board:
Radeon HD 5970 reviewed (7) [Source: view picture gallery]
Radeon HD 5970 reviewed (9) [Source: view picture gallery]
Radeon HD 5970 reviewed (12) [Source: view picture gallery]
Like it has been on the predecessors the two graphics chips are placed on the same side of the PCB, surrounded by 1 GiByte GDDR5 video memory each. One half of the VRAM is placed on the front and the other on the rear side of the card. Like on all versions of the HD 5000 series the memory comes from Hynix's TC2 selection which is specified up to 2,500 MHz (0.4 nanoseconds access time). So the VRAM on the HD 5970 is noticeably underclocked.
The cooler is equipped with a optical simple but mighty Vapor Chamber, which can deal with a waste heat of up to 400 watt - says Ati. Fresh air is supplied by the same radial fan with 0.8 ampere known from the HD 5800 cards. A thick baseplate and a metal backplate cover GPUs, memory, VRMs and the bridge chip. Radeon HD 5970 reviewed: Power consumption and Loudness
The results of the Radeon HD 5970 are quite good - for a dual GPU card. In idle mode it is quite (1.1 Sone) but reaches up to 5.5 Sone when stressed with gaming workload. This is definitely audible. If the card is really stressed, with Furmark or active Supersampling for example, the loudness can reach even higher levels.
The power consumption of the HD 5970 on the other hand is worth-seeing. In idle mode the card clocks itself down and deactivates, according to AMD, the secondary GPU. But apparently the memory and other components remain active since 45 are still more than 28 watt. But at least the 74 watt of the Radeon HD 4870 X2 and the 59 watt of Nvidia's Geforce GTX 295 are beaten noticeably. Radeon HD 5970 reviewed: Overclocking
Our sample was sent directly by AMD and thus does not necessarily represent the overclocking behavior of retail graphics cards. Nevertheless we were able to run 820/2,300 MHz stable at 50 percent fan speed (almost 10 Sone loudness!). This increases the gaming performance by about 10 percent.
Radeon HD 5970 reviewed (56) [Source: view picture gallery]
Courageous overclockers might be able to achieve even higher results be increasing the GPU voltage with tools like MSI's Afterburner. The average value of our sample (and most likely of most other 5970s) was set to 1.05 volt per GPU. Afterburner allows to go up to 1.3 volt - but we strongly advise against this because the thermal dissipation loss would exceed 400 watt by far and the components would run out of spec.