Is An Overclocked Radeon HD 7970 Greater Than GeForce GTX 680?
Can you believe the Radeon HD 7970 was introduced six months ago? In those 180 days, we’ve seen AMD claim the single-GPU performance crown, flesh out an entire family of graphics cards based on its capable GCN architecture, and then lose its fastest-in-the-world title to Nvidia’s GeForce GTX 680. I’m working on a script for the movie.
Along the way, though, we’ve wondered about the company’s approach to pricing. Even after Nvidia launched a faster, less expensive card, AMD kept selling its Radeon HD 7970 for $550. It eventually shaved off $70, only to see the competition kick out an even cheaper board (GeForce GTX 670) able to rout the 7970 in most games.
At no point was AMD’s flagship ever a bad card, though. Its dominance was simply contested quickly—and frustratingly—by a competing piece of hardware suffering such poor availability that you had to sign up for notifications just to catch it in stock. Although 680s are in stock now, as recently as a couple of weeks ago they were mostly a threat on paper. But the GeForce GTX 670 has always been a lot more accessible at $400, putting the Radeon HD 7970 under significant pressure. Certain 7970s are even down as low as $450.
To the point, with the maturation of TSMC’s 28 nm manufacturing process, AMD is discovering that a greater number of its Tahiti GPUs are running stably at higher core clock rates. Now, we already knew that the Radeon HD 7900s overclocked well. But rather than leaving extra performance on the table for enthusiasts to exploit on their own time, the company is unveiling a Radeon HD 7970 GHz Edition card that purportedly one-ups Nvidia’s GTX 680 and gives AMD a reason to push prices back up.
Meet The Radeon HD 7970 GHz Edition
Physically, this is the Radeon HD 7970 you already know. Put AMD’s reference GHz Edition card next to the one launched six months ago and you can’t tell them apart. What few differences there are all materialize under the card’s 11”-long fan shroud.
Most obvious is a higher core clock rate. Officially, AMD lists it at 1000 MHz—a bump up from the original version’s 925 MHz frequency. But it also enables a higher 1050 MHz P-state that the GPU favors when thermal headroom allows. AMD is marketing this combination of clock rates as PowerTune with Boost.
If you’re not already familiar with what PowerTune is or how it works, I break it down in my Radeon HD 6970 and 6950 review. Basically, though, AMD confirmed for us that PowerTune with Boost is the same exact thing, plus the ability to dynamically increase voltage. The company says its 1 GHz clock is fixed, and altering Overdrive’s frequency slider only changes the maximum boost level.
But it seems like you could also describe the 7970 GHz Edition as a 1.05 GHz card that, subjected to a synthetic power load like FurMark, drops 50 MHz and some voltage to not violate its TDP. After all, that’s what PowerTune has done for a year and a half.
The other performance enhancement comes courtesy of faster memory. Back when AMD launched the Radeon HD 7970, it “only” had access to 1375 MHz GDDR5 modules. On a nice, wide 384-bit bus, they were good for 264 GB/s of aggregate bandwidth. Now it’s using 3 GB of 1500 MHz modules on the same bus to push 288 GB/s.
| Header Cell - Column 0 | Radeon HD 7970 GHz Edition | Radeon HD 7970 | GeForce GTX 680 |
|---|---|---|---|
| Stream processors | 2048 | 2048 | 1536 |
| Texture Units | 128 | 128 | 128 |
| Full Color ROPs | 32 | 32 | 32 |
| Graphics Clock | 1000 MHz Base / 1050 MHz Boost | 925 MHz | 1006 MHz |
| Texture Fillrate | 134.4 Gtex/s | 118.4 Gtex/s | 128.8 Gtex/s |
| Memory Clock | 1500 MHz | 1375 MHz | 1502 MHz |
| Memory Bus | 384-bit | 384-bit | 256-bit |
| Memory Bandwidth | 288 GB/s | 264 GB/s | 192.3 GB/s |
| Graphics RAM | 3 GB GDDR5 | 3 GB GDDR5 | 2 GB GDDR5 |
| Die Size | 365 mm2 | 365 mm2 | 294 mm2 |
| Transistors (Billion) | 4.31 | 4.31 | 3.54 |
| Process Technology | 28 nm | 28 nm | 28 nm |
| Power Connectors | 1 x 8-pin, 1 x 6-pin | 1 x 8-pin, 1 x 6-pin | 2 x 6-pin |
| Maximum power (TDP) | 250 W | 250 W | 195 W |
| Price | $500 MSRP | $450 Street | ~$520 Street |
AMD acknowledges that the Tahiti GPU itself is exactly the same. If you want the skinny on that, feel free to reference back to our Radeon HD 7970 launch coverage. Everyone else, let’s move on to a deeper analysis of PowerTune with Boost.
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