Nvidia's GeForce GTX 460M
With a die size less than half that of the GeForce GTX 480M, the GTX 460M’s 1.5 GB memory configuration could leave some users confused about its origins. A little poking around with GPU-Z helps shed some light on the internals.
Like the mobile parts that came before it, Nvidia sources its GTX 460M GPU from the desktop lineup, in this case the now-familiar GF106 previously found on the GeForce GTS 450. But how did the desktop card end up with 1.0 GB memory if capacities are limited to bus width multiplied by exponents of two?
| Desktop vs Mobile GeForce Graphics | |||
|---|---|---|---|
| Row 0 - Cell 0 | Desktop GeForce GTX 460 | Desktop GeForce GTS 450 | GeForce GTX 460M |
| Transistors | 1.95 billion | 1.17 billion | 1.17 billion |
| Engine Clock | 675 MHz | 783 MHz | 675 MHz |
| Stream Processors | 336 | 192 | 192 |
| Texture Units | 56 | 32 | 32 |
| ROP Units | 32 | 16 | 24 |
| Compute Performance | 907 GFLOPS | 601 GFLOPS | 518 GFLOPS |
| DRAM Type | 1.0 GB GDDR5-3600 | 1.0 GB GDDR5-3206 | 1.5 GB GDDR5-2500 |
| DRAM Interface | 256-bits | 128-bits | 192-bits |
| Memory Bandwidth | 115.2 GB/s | 57.7 GB/s | 60.0 GB/s |
| Module TDP | 160W | 106W | 65W |
The desktop GeForce GTS 450 has been handicapped by Nvidia, in spite of what we were told at launch. The back-end was formerly limited to 16 ROP units and a 128-bit interface. The memory capacity difference now makes sense, because 128 x 8 equals 1024, and 192 x 8 equals 1536.
The added ROP units make it appear as though the GeForce GTX 460M might be a little more powerful than the desktop GeForce GTS 450, but a lower clock speed on an identical number of stream processors more than makes up the difference. The GTX 460M ends up short of the GTS 450, in spite of its extra bandwidth. But that’s probably fine with Nvidia since the desktop part often performs on par with the super-expensive GeForce GTX 480M.
Aside from what appears to be a huge performance deficit compared to the desktop GeForce GTX 460, the best reference point for GTX 460M performance could be the GTX 480M. With twice the memory bandwidth and twice the die size, Nvidia's GTX 480M undoubtedly costs more to manufacture than the GTX 460M. We checked the prices of two major vendors to find out how much a single-card to dual-card upgrade costs, in an effort to determine the cost-per-card built into each notebook.
| Mobile Graphics Module Prices (Upgrade from Single to Dual GPU) | |||
|---|---|---|---|
| Row 0 - Cell 0 | GeForce GTX 480M | Mobility Radeon HD 5870 | GeForce GTX 460M |
| Die Size | 529 mm² | 170 mm² | 238 mm² |
| Memory | 2 GB GDDR5-2400 | 1 GB GDDR5-4000 | 1.5 GB GDDR5-2500 |
| Module Price | $588 | $382 | $213 |
Before we even begin testing, the smaller part looks like it could provide a huge value benefit. The GeForce GTX 460M costs less than half the price of a GTX 480M, though higher yields on the smaller part could potentially account for the difference.
