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GeForce GTX 750 Ti Review: Maxwell Adds Performance Using Less Power

Power Consumption: Gaming

Benchmark System And Procedure

We collaborated with HAMEG (Rohde & Schwarz) to upgrade our power consumption measurement system. It’s now one step away from being complete and will be continuously refined.

We record all channels and the corresponding oscilloscope value/curves for our measurements. The very precise and (more important) fast current clamps yield 100 mV/A, making it easy to calculate power based on the voltage. We also record the supply voltage to multiply its value with the recorded amperage. Depending on the resolution we choose, this procedure yields a very detailed power consumption history. We generally set this to 1 ms, allowing us to capture all fluctuations attributable to AMD’s PowerTune or Nvidia’s GPU Boost technology.

Measurement Procedure:Non-Contact Direct Current Measurement at the PCIe Slot Non-Contact Direct Current Measurement at the External PCIe Power Supply Direct Voltage Measurement 3.3 V / 12 V
Measurement Apparatus:Oscilloscope: HAMEG HMO1024 Four-Channel Digital Oscilloscope with Memory and Ethernet Remote ControlPower Clamp: HAMEG HZO50 (1 mA-30 A, 100 kHz DC, Resolution 1 mA)Voltage Divider Probe: HAMEG HZ154 (1:1, 1:10), Assorted AdaptersDigital Multimeter: HAMEG HMC8012
Bench Table:Microcool Banchetto 101
Test Hardware:Intel Core i7-3770K (Ivy Bridge), Overclocked to 4.5 GHzCorsair H100i Compact Water Cooling Solution16 GB (2 x 8 GB) Corsair Vengeance DDR3-1866Gigabyte G1 Sniper 3 + Modified PCIe Adapter with Current Loops
Power Supply:Corsair AX860i with Modified Plugs (Pickups)

Power Consumption: Gaming

We're particularly interested to learn how Nvidia improved the efficiency of its architecture. In terms of total power consumption, the card averages (in a warmed-up condition, after applying full load) just a little bit over the GPU's TDP. This measures the whole card though, including memory. Thus, Nvidia keeps its word and clearly sets a new standard for performance per watt.

For the first time ever, the average power figure isn't centered between minimum and maximum values, but rather closer to the bottom of the chart. Peaks are clearly rarer, but they're also more extreme. This is important because the card is driven by the motherboard's PCI Express slot, making the platform's quality more important than it might otherwise be.

Because the 170-second run is hard to display at the resolution we used, here's a 10-second break-out for additional detail:

The snippet illustrates how important fast measurements are to the average power consumption value. Of course, we can get even more precise, so this next graph represents just one second. Fluctuations in draw effectively demonstrate what your power supply has to be capable of handling.

But how does consumption change when you take into account more use cases?