A few days ago at the PC Gaming Show event during E3, AMD CEO Lisa Su revealed the RX 460 and RX 470 graphics cards for the first time. The days of seemingly-endless Pitcairn rebrands are over: these cards, along with the RX 480 that was already revealed at Computex, will all be based on AMD's new Polaris graphics architecture. This is good news for AMD and for the market, and today we have some information on these cards courtesy of a deck of slides from AMD.
The slide above confirms most of what we already knew or suspected about Polaris 10: 36 GCN compute units and a 256-bit memory interface. Those 36 CUs translate to 2,304 shader processors, putting Polaris 10 squarely between the Radeon R9 380x and R9 390 in terms of shader count. The specs match entirely with what we know about the Radeon RX 480.
However, buried in those same slides is some benchmark data justifying the "2.8x perf/watt" claim. AMD claims to have tested a 110-watt RX 470 versus a 180-watt R9 270X to come up with that figure. The little 110-watt GPU scores an impressive 9090 in 3DMark Fire Strike 1080p, and manages an average 46 FPS in Ashes of the Singularity (1080p High preset), a 60-FPS average in Hitman (1080p High), and 121 FPS in Overwatch (1080p Max). Based on that kind of performance, we feel comfortable saying the RX 470 is based on some permutation of the Polaris 10 chip in the RX 480.
The RX 460, then, is likely based on the smaller Polaris 11 chip that until now was just a big question mark. AMD said in the past that Polaris 11 would not require an additional power connector, and indeed the board that Lisa Su showed at E3 lacked one. As it happens, Polaris 11 is a much smaller chip than its big brother, with only 16 CUs and half the memory interface width. Lest you become discouraged, remember that the GeForce GTX 960 also wields a 128-bit memory interface. Some back-of-the-envelope math based on the 2 TFLOPs performance AMD is touting suggests a clock rate around 1GHz for this chip.
AMD is making that same 2.8x performance-per-watt claim about Polaris 11, and there's benchmark data for it, too. Instead of the RX 460 that Ms. Su showed off, however, the company tested an "RX 480M," the first mention we've seen of that chip. The company says the RX 480M with 16 CUs is a 35W part that scores 7200 in 3DMark 11 and 4070 in 3DMark Fire Strike. This was compared to a Bonaire-based 82-watt R9 M280X with 14 CUs that scored 5700 and 3500 in those same tests.
These performance comparisons have little context and come straight from AMD, so they are best taken with a handful of salt. Still, taken at face value, the numbers are impressive. The 46 FPS average in Ashes of the Singularity puts the RX 470 squarely in R9 390 and GTX 970 territory, although some of that is likely the result of driver improvements since our test. Depending on the gap between the 470 and the 480, Polaris could be quite the coup for AMD. We'll see on the 27th.