R9 280X: The Tahiti GPU’s Second (Or Third?) Lease On Life
I guess it depends whether you consider the Radeon HD 7970 GHz Edition a distinct product introduction. If so, then R9 280X is the third single-GPU graphics card sporting AMD’s complete Tahiti GPU.
When I wrote AMD Radeon HD 7970 GHz Edition Review: Give Me Back That Crown!, that card featured a base clock rate of 1 GHz that’d jump to 1.05 GHz under the effects of PowerTune with Boost. Otherwise, it employed Tahiti in its uncut form—with 2048 Stream processors, 128 texture units, 32 ROPs, and a 384-bit aggregate memory bus populated with 3 GB of GDDR5 at 6 GT/s. AMD slapped a 250 W maximum board power on the card and started shipping it at $500 (already down $50 from the original 7970’s launch).
The R9 280X’s specs are very, very similar. Its Tahiti GPU boasts the same 2048:128:32 configuration, with a 384-bit memory bus rocking 3 GB of GDDR5 that AMD says should operate at 6 GT/s. You’ll need to use the same six- and eight-pin connectors for an identical 250 W board power. The one notable difference is the 280X’s engine clock, which tops out at 1 GHz. As a result, you’ll notice the R9 280X performing slower in our benchmarks. Fortunately, there’s that price drop…
At $300, an R9 280X does battle against the GeForce GTX 760, mostly. I say mostly because the cheapest 770s are selling for around $400 (clearly too high to be in the same league), while the 760s are between $250 and $320. And since we already know the Radeon HD 7970 GHz Edition and GeForce GTX 770 are the cards that trade blows, well, AMD should be in a pretty strong position by the time we get to the end of our benchmarks.
To answer whether existing Radeon HD 7970 cards can be paired with the new R9 280X, yes, they work together. A quick Fraps-based test showed one 280X hitting 52.9 FPS in Battlefield 3 at 2560x1440. Dropping a 7970 GHz Edition next to the newer board pushed frame rates to 102.3 FPS. When it wasn't in use, the 7970 properly spun down according to AMD's ZeroCore technology.
We received two different takes on the R9 280X, neither of them conforming to AMD’s reference design.
The first card was Asus’ R9 280X DirectCU II TOP, an overclocked board with a GPU capable of up to 1070 MHz and GDDR5 memory at 6400 MT/s. According to Asus, it’ll sell this variant for $310, bundled with a power adapter and CrossFire cable.
Beyond the tweaked specifications, Asus employs a non-reference PCB and oversized cooling to help manage power, thermals, and acoustics. The company says AMD’s reference 280X employs a five-phase (60 A/phase) PWM, while its own card features eight phases at 45 A/phase. This, along with claimed higher-quality power components, is supposed to benefit aggressive overclocking. Naturally, Asus bundles its GPU Tweak software for adjusting core clock, voltage, memory, power target, and fan speed (mostly settings you can tune in AMD’s OverDrive applet, except for voltage).
Although the R9 280X DirectCU II TOP is a dual-slot card, it’s also long and tall. The fan shroud stretches over the back of the PCB, imparting an 11.2” overall length. Further, a heat pipe coming out of the board’s top increases maximum height to 5.7”.
Display outputs include one dual-link DVI-I port, one dual-link DVI-D connector, HDMI, and a full-sized DisplayPort ouput.
XFX’s R9-280X-TDFD showed up next, based on a slightly different PCB. This is the one we benchmarked for our performance evaluation, if only because we were able to get its speeds and feeds first. An 850 MHz core clock rate accelerates up to 1 GHz when the thermal headroom allows. The memory tops out at AMD’s reference 6 GT/s, serving up to 288 GB/s of bandwidth.
Otherwise, the R9-280X-TDFD is a dual-slot board employing two axial-flow fans that do their job very quietly, but dump waste heat back into your case instead of exhausting it out the back.
Display outputs total five. You get one dual-link DVI-I port, one single-link DVI-D connector, HDMI, and two mini-DisplayPort outputs. Quad-card CrossFire configurations are supported across two bridges, though an extra-tall plastic frame surrounding the heat sink makes even a flexible ribbon connector difficult to attach.