When ATI launched the HD4870 graphics card, it surprised many with its blend of near high-end performance with mainstream prices. One of the most surprised seemed to be arch enemy Nvidia, which promptly started chopping prices to try to compete on the bang-for-buck front.
So if one HD4870 is good, imagine how good two HD4870 cores on the same PCB might be. Welcome to the R700 - or, to you and me, the Radeon HD4870 X2.
From the outside the only apparent difference between the new HD4870 X2 and the previous HD3870 X2 is the pair of updated RV770 cores and faster GDDR5 memory, but under the skin there is a whole world of difference.
The HD4870 has the second generation PCI-E 2.0 x16 switch (PLX) as opposed to the PCI-E 1.1 of the previous generation X2, giving the HD4870 a much wider communication channel than before; twice as big, in fact, at 5GB/s (in each direction).
This helps in the rendering of modern games, as these need data transfers between each GPU when more than one core is used. In addition to this fast, wide interconnect, the HD4870 X2 also supports SidePort which enables the cores to use an additional 5GB/s bi-directional bandwidth, but seeing as though no software currently available takes advantage of this, it has been disabled. This all adds up to a theoretical internal bandwidth of a colossal 21.8GB/s, eliminating any potential bottlenecks.
Although the HD4780 X2 comes with 2GB of GDDR5 memory, dual GPU cards don't share a frame buffer which means in this case that each RV770 core has 1GB of GDDR5 to play with. The memory may only go through a seemingly mean 256-bit memory bus, but the sheer speed of GDDR5 (in this case 3,600MHz) more than makes up for it. Each core is clocked at 750MHz and the 800 shaders in each all run at the same speed as the core.
Surprisingly, the HD4870 X2 uses less power than two HD4870s in a Crossfire set up. The two-card set up will eat up to around 320W while the HD4870 X2 makes do with 'just' 286W. As with the single card it uses single 6-pin and 8-pin PCI-E power connectors.
Sapphire's board is pretty much a reference design in red and black but with the company's own attractive gunslinger sticker on the dual-slot cooler. This cooler doesn't use heatpipe technology to aid in the cooling process, relying instead on two hefty copper heatsinks, one on each GPU.
The card uses the same fan as found on the single core model and our review sample had a strange habit of spinning the fan up to full speed for a split second for no apparent reason, sometimes while being benched, sometimes just while in idle mode.
So what about performance, I hear you ask? Well, it's pretty - no, make that very - impressive, especially as you might expect at higher resolutions when all that bandwidth makes its presence felt.
Testing it with 3DMark06 at a resolution of 1,280 x 1,024 it produced a score of 16,400, compared to the 13,980 of a single HD4870 and 14,102 of an Nvidia GTX280. But of course with all that available bandwidth the real grunt of the HD4870 X2 comes into play at higher resolutions. At 1,920 by 1,200 the X2 gives a score of 15,890 compared to the 12,758 of the HD4870 and 13,400 of the GTX280. It's a similar story in the more intensive 3DMark Vantage: the X2 produced a score of 12,530 in the Performance test as compared to the 8,360 of the HD4870 and 10,103 of the GTX280.
It's the same story again when tested using real games: at high resolutions and with plenty of filtering added, the HD4870 X2 is out on its own. In World in Conflict at a resolution of 2,560 by 1,600 with 4x AA and 16x AF, the average frame rate produced by the HD4870 X2 was 45fps while the single core HD4870 and GTX280 could only manage 26fps and 33fps respectively.
If you want to test your own setup, Sapphire now bundles 3DMark Vantage in with the card instead of the previous 3DMark06. Along with it you get CyberLink's DVD Suite and PowerDVD and the latest version of the Ruby Rom. The hardware bundle consists of two power adaptors (one 4-pin Molex to 6-pin PCI-E and one 4-pin Molex to 8-pin PCI-E), a single CrossFire bridge, S-Video to RCA adaptor, Component out dongle, DVI-VGA adaptor and a DVI-HDMI adaptor.
Sapphire - Radeon HD4870 X2 features - Verdict
While Nvidia may still hold the crown for the fastest single core card in the GTX280, the Radeon HD4870 X2 shows that ATI is interested at getting back the overall performance crown, and in most respects has succeeded with the new card. All this at a price point that isn't too outrageous compared to the price that some GTX280s are going for.
