Review AMD Radeon HD 6870 CrossfireX: More Performance for Less

In our first article on the HD 6870, our discussions revolved around its performance in games. The card did very good in some titles, while in some others, such as Metro 2033, we’re still not quite satisfied by the amount of frames per second produced by this card. It would, therefore, be really nice if we could multiply its processing power.

One logical way to improve performance significantly is by adding another HD 6870 and run the pair in multi-graphics configuration, which is relatively easy to do since the card has native CrossfireX support. How much additional performance can you expect from this multi-card setup anyway? We’ll get to that, but first, let’s examine the technical specs first.

Specification

	AMD Radeon HD 6870	AMD Radeon HD 6850
Codename	Barts XT	Barts Pro
Fabrication Process	40 nm	40 nm
Transistors	1.7 Billion	1.7 Billion
Die Size	225 mm2	225 mm2
Core Clock	900 MHz	775 MHz
Stream Processors	1120	960
Texture Units	56	48
ROPs	32	32
Memory Type	GDDR5	GDDR5
Memory Size	1024 MB	1024 MB
Memory Clock (effective)	4200 MHz	4000 MHz
Memory Interface	256-bit	256-bit
DirectX Version	11	11
Shader Model	5	5
Power Connectors	2x 6-pin	6-pin
Min Recommended Power Supply	500 Watt	500 Watt
Bus Support	PCIe 2.1 x16	PCIe 2.1 x16

CrossfireX Setup

You need at least two Radeon cards for CrossfireX setup. While not required, it would be better if both cards are identical. You will also need a motherboard with two PCIe x16 slots. Crossfire support is available on Intel motherboards based on the series 5 and 4 chipset families. It is also supported by motherboards based on more recent AMD chipsets (series 8 and 7).

Connect the two Radeons using a CrossfireX Bridge placed on top of the cards.

You will also need at least a 600 Watt power supply with four, 6-pin PCIe connectors.

When both cards have been properly positioned in their slots, it’s time to install the driver software. CrossfireX will be detected and activated automatically.