Power Consumption: Better, But...
One of the critical areas in the battle between the 9400M and the 945GC was the overall power consumption of the platform. Unfortunately, we had difficulty measuring power use because the reference Ion platform and the D945GCLF motherboard use very different power supplies. On the Ion, an external power brick converts AC power to 12 V DC, which is then divided into several voltages—3.3 V, 5 V and 12 V—by the motherboard power stage. And since we measure power consumption at the AC outlet, we need to know the output both of the brick and of the power stage on the motherboard.
Nvidia wasn’t able to give us any information, and we didn’t have the necessary equipment for taking measurements at the time of the test. Fortunately, though, the brick used by Nvidia has been tested by our confreres at SilentPCReview. To be more exact, they made careful measurements of the brick’s efficiency with a 12 V DC -> 12 V, 5 V, 3.3 V DC converter, so their figures are a good estimate of the output of the Ion’s power supply. The power-use values shown below were calculated based on the results of SPCR’s test. We should make it clear that they should be taken for what they are, since there are many sources of possible variations. But they’re the best approximation we’re able to make at the present time.
In contrast, the Intel D945GCLF motherboard employs a traditional ATX AC/DC power supply. We used a low-power PSU in order to ensure good efficiency at very low loads. Our choice was an FSP/Sparkle Power SPI220LE, which we’d already used in our earlier tests of the Atom. This power supply has also been tested by SPCR, using the same protocol as for the preceding components, so we felt it was a good idea to again use their figures, to avoid introducing errors.
| Header Cell - Column 0 | Efficiency, Sparkle Power PSU | Efficiency, Ion Platform Power Supply | ||
|---|---|---|---|---|
| Row 0 - Cell 0 | Consumption at the AC outlet (W) | Efficiency (%) | Consumption at the AC outlet (W) | Efficiency (%) |
| SPCR Measurement | 26.3 | 73 | 28.3 | 77.7 |
| 40.8 | 77.7 | 47 | 85.6 | |
| Extrapolation | 23 | 71.9 | 15 | 72.1 |
| 32.7 | 75.1 | 25.9 | 76.7 |
| Header Cell - Column 0 | Consumption at the AC Outlet (W) | Actual Calculated Consumption (W) | Ion Advantage (%) | ||
|---|---|---|---|---|---|
| Row 0 - Cell 0 | Ion | D945GCLF | Ion | D945GCLF | |
| No Load | 15 | 23 | 10.8 | 16.5 | -34.6 |
| Peak Load | 25.9 | 32.7 | 19.9 | 24.5 | -19.1 |
The bottom line, granted the suppositions we’ve made, is that the Ion platform proved to be substantially more economical than the basic Intel platform. We estimate its advantage as being between 19% and 35%, depending on whether PC is idle or under load. These results are in line with the theoretical TDPs cited by the manufacturers, but they’re still a little surprising: the GeForce 9400M has a TDP of only 12 W, compared to 25.5 W for the 945GC + ICH7 tandem, so we expected a bigger difference.
To be sure of just how much more energy-efficient the Ion is compared to the Intel platform, we’ll need to run tests under conditions that make for better comparison. It shouldn’t be long until we can; Nvidia tells us that Ion motherboards in micro-ATX or mini-ITX formats will available soon, so we’ll get back to you in a few weeks. But we can already say that the Ion is clearly a more energy-efficient platform than the standard Atom platform.