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The cards
The faster of the two newcomers, the $349 Radeon HD 7870 GHz Edition, uses the Pitcairn GPU with all of its bits and pieces enabled. AMD clocks it at 1,000MHz, hence the GHz Edition suffix, and accompanies it with 2GB of GDDR5 memory set to operate at 1200MHz (for an effective peak transfer rate of 4800 MT/s). The card has a 190W power envelope, but AMD says "typical" power consumption is 175W.

The card is about 9.7" (247 mm) long and requires a couple of six-pin PCIe power connectors. Our sample came with a copper-and-aluminum heatsink covered by one of AMD's trademark Batmobile-inspired shrouds. A blower draws air from inside the case, through the heatsink fins, and outside the case via a vent in the port shield.

Speaking of connectors, the 7870 has the exact same port arrangement as the Radeon HD 7900 series: two mini DisplayPort outputs, one HDMI output, and one dual-link DVI port. AMD says the card supports up to six displays, but that's only possible with a DisplayPort hub—and those are hard to come by, if not unavailable entirely.

The $249 Radeon HD 7850 is also Pitcairn-based, but it's had a mild lobotomy to keep it from nipping at its sibling's heels too much. Four of its 20 compute units have been disabled, leaving it with 1024 stream processors and 64 texture units. The core clock speed has been lowered to 860MHz, as well. Happily, other resources have gone unharmed. The 7850 also enjoys the exact same memory configuration as the 7870.

You may have noticed that our 7850 and 7870 samples look an awful lot alike, save for the "1GHz Edition" sticker on the latter. That's because the two cards have the same circuit board and the same cooler. However, AMD tells us retail Radeon HD 7850s will be different. They'll have shorter, stubbier circuit boards and matching third-party heatsinks and fans. Here's one, built by Sapphire:


Source: AMD.

Another key difference is the 7850 only requires a single six-pin power connector. That's true even for our sample:

According to AMD, the 7850 has a 150W TDP and typical power draw of around 130W. That's 40-45W less than the 7870.

Ready to move on to the benchmarks? Not so fast. We have a big, meaty table full of peak theoretical numbers for you to pore over first:

  Peak pixel
fill rate
(Gpixels/s)
Peak bilinear
filtering
(Gtexels/s)
Peak bilinear
FP16 filtering
(Gtexels/s)
Peak shader
arithmetic
(TFLOPS)
Peak
rasterization
rate
(Mtris/s)
Memory
bandwidth
(GB/s)
GeForce GTX 560 Ti 26 53 53 1.3 1644 128
GeForce GTX 560 Ti 448 29 41 41 1.3 2928 152
GeForce GTX 570 29 44 44 1.4 2928 152
GeForce GTX 580 37 49 49 1.6 3088 192
Radeon HD 6870 29 50 25 2.0 900 134
Radeon HD 6950 26 70 35 2.3 1600 160
Radeon HD 6970 28 84 42 2.7 1760 176
Radeon HD 7850 28 55 28 1.8 1720 154
Radeon HD 7870 GHz Edition 32 80 40 2.6 2000 154
Radeon HD 7950 26 90 45 2.9 1600 240
Radeon HD 7970 30 118 59 3.8 1850 264

Thanks to its 1000MHz clock speed, the Radeon HD 7870 has higher pixel fill and rasterization rates than even the Radeon HD 7970. That's because the two cards have the same number of ROPs, and they can both process two triangles per clock, but the 7970 is only clocked at 925MHz. The 7870 does have more modest texture filtering capabilities, though, not to mention substantially lower shader throughput and memory bandwidth.

Compared to the old Radeon HD 6970, which carried the same $349 price tag before it started mysteriously disappearing from Newegg's stock, the 7870 looks rather good. Some of its theoretical peaks are slightly higher, and some are slightly lower, but keep in mind Pitcairn should be more efficient than the 6970's Cayman chip.

Getting a feel for the contest between the 7870 and the GeForce GTX 570 is a little harder, but as we said on the previous page, the new Radeons are not ill-equipped. The same can be said about the matchup between the 7850 and the GTX 560 Ti—in that matchup, the 7850 is better outfitted in all but peak FP16 texture filtering. The GeForce's ability to do FP16 filtering at the same speed as it handles integer formats speed gives the GTX 560 Ti a sizeable advantage there over the Radeon HD 7850.

Will our benchmark results confirm our expectations? Let's find out.