Mobile Model Shenanigans: What's In A Name?
Power consumption is the big neutralizer when it comes to separating desktop and mobile component design. As you know, power is dissipated as heat, and heat is public enemy number one. We certainly can’t walk around with three-inch-thick notebooks that consist of more copper than component space and require desktop-sized power supplies. Even if such a device were portable, we surely wouldn't want it resting on our...laps.
So, we're not unreasonable here. The idea that certain pieces of hardware have to be downclocked before they're deemed suitable in notebooks is acceptable to us.
But then came the naming games. The earliest any of us can remember a mobile part being upgraded (in spirit, at least) to an inflated model name was when ATI’s Radeon 9600 XT magically turned into the much larger Mobility 9700. ATI could have excused that move with the explanation that the Radeon 9600 XT outperformed an underclocked Radeon 9700 desktop GPU at similar power levels, but that was just the beginning of a long journey down the rabbit hole.
Stranger the naming became, until we finally ended up with underclocked upper-mainstream gaming GPUs getting the names of their extreme counterparts in the Radeon HD 6970M and GeForce GTX 580M. But all of that paled in comparison to one of AMD’s most recent mobile releases, the single-GPU Radeon HD 6990M.
You might expect the 6990M to consist of two Radeon HD 6970M GPUs, since that's how we get a desktop-class Radeon HD 6990.
Instead, we see AMD switch from an underclocked version of its Radeon HD 6850 to an underclocked version of its Radeon HD 6870. Whereas the desktop Radeon HD 6990 has almost two times the raw computational power of the Radeon HD 6970, the 6990M gains less than 25% over AMD's 6970M.
| Desktop vs Mobility Radeon Graphics | ||||
|---|---|---|---|---|
| Row 0 - Cell 0 | Desktop Radeon HD 6990 | Desktop Radeon HD 6970 | Radeon HD 6970M | Radeon HD 6990M |
| Transistors | 5.28 billion | 2.64 billion | 1.7 billion | 1.7 billion |
| Engine Clock | 830 MHz | 880 MHz | 680 MHz | 715 MHz |
| Shader (ALUs) | 3072 | 1536 | 960 | 1120 |
| Texture Units | 192 | 96 | 48 | 48 |
| ROP Units | 64 | 32 | 32 | 32 |
| Compute Performance | 5.1 TFLOPS | 2.7 TFLOPS | 1.3 TFLOPS | 1.60 TFLOPS |
| DRAM Type | GDDR5-5000 | GDDR5-5500 | GDDR5-3600 | GDDR5-3600 |
| DRAM Interface | 256-bits per GPU | 256-bits | 256-bits | 256-bits |
| Memory Bandwidth | 160 GB/s per GPU | 176 GB/s | 115.2 GB/s | 115.2 GB/s |
| TDP | 375 W | 151 W | 75 W | 100 W |
Both AMD and Nvidia excuse this naming disparity by affixing their flagship desktop model name to their flagship mobile products. However, we see this as a great way to deceive uninitiated notebook buyers. After all, the performance profile of each desktop GPU is trumpeted to the masses before the notebook GPUs with similar names are introduced. So, “common knowledge” works against the partially-informed buyer.
Man, just imagine if Intel called its mobile flagship the Core i7-3960XM. Though, at $1050, the four-core, 2.7 GHz Core i7-2960XM is only one digit away from following along...
Amidst all of this, some say that the other limitations of mobile computing make additional GPU power unnecessary. Notebook screens are relatively small, with moderate resolutions that typically don’t require as much graphics horsepower to drive. Although they exist, we haven't yet tested any mobile gaming platforms capable of spanning across three screens via Eyefinity or Surround, and single-screen resolutions as high as 1920x1080 aren't particularly taxing on today's graphics processors.
Nevertheless, today we’ll we compare the real performance differences between desktop and notebook GPUs while testing within the limits of a real high-end desktop replacement notebook.
