NVIDIA GeForce4 440 Go

Although the user selectable aspect of PowerMizer is disabled on all laptops currently shipping, NVIDIA provided us with a registry key that would enable this feature on our test laptop. We already discussed what is going on technologically with PowerMizer; what we were curious about was what kind of difference PowerMizer made.

Before we got to testing, we were curious to see what the PowerMizer software control did to the power of our chip. As we mentioned before the PowerMizer slider has three positions: Maximum Performance, Balanced and Maximum Power Savings. Each position on the slider corresponds to a different clock speed that the GeForce4 Go can run at. When an OEM implements PowerMizer, it is up to them what clock speed each stop will correspond to. Since Dell does not support this PowerMizer feature, it was up to NVIDIA this time. In the case of our discrete GeForce4 440 Go, the following clock speeds were used:

Maximum Performance: 220MHz core, 440MHz memory
Balanced: 200MHz core, 400MHz memory
Maximum Power Savings: 100MHz core, 250MHz memory

As can be seen, the clock speed difference between the maximum performance setting and the maximum power savings setting is fairly significant. We are typically left with guessing how much difference a power saving technology makes in a notebook, but thanks to NVIDIA we were able to find out.

Along with the sample notebook that NVIDIA sent us, the company also included an inline test device that allowed us to measure the power consumption of the notebook and see how it altered under different PowerMizer states. The multimeter is hooked into the inline test board that intercepts the power signal between the notebook and the AC adapter. Switching our multimeter to measure amps, we were able to measure the system's current draw in any situation. To eliminate the draw placed on the AC adapter during battery charging, measurements were taken with the system battery removed.

Our system used a 1.6GHz Pentium 4-M chip with enhanced SpeedStep technology. As a result, the test laptop was always throttling between the 1.6GHz and 1.2GHz, just as it would if it were on battery power. We monitored the system current draw under various situations to examine exactly how PowerMizer affected battery life.

To calculate power consumption out of the current draw, we can use p = v*a which states that power consumption in watts is equal to volts times amps. Let's see how power consumption of the GeForce4 440 Go varied depending on PowerMizer state.

To test power drain in a gaming situation, we monitored the current draw during the Unreal Performance Test 2002 build 856 benchmark run at 1024x768x32, a resolution we consider to be a moderate gaming resolution. The maximum current draw was recorded in each of the three PowerMizer states with the following results.

Power Consumption in 3D Gaming (watts) Maximum Battery Life Balanced Maximum Performance 52.2 55.2 58.4 | 0 | 12 | 23 | 35 | 47 | 58 | 70

So, under a stressful 3D gaming situation, PowerMizer provided us with an 11.9% decrease in power consumption. This is clearly a fairly large number considering that 11.9% decrease in consumption is of the whole system's power consumption. In a minute we will get to how this related to real world battery life.