Nvidia GeForce GTX 970 And 980 Review: Maximum Maxwell

Power Consumption In Detail

Idle Power Consumption

[EDIT] Our original Nvidia GeForce GTX 980 reference sample suffered from a BIOS issue that caused a higher-than-expected power draw. We flashed the card with the reference BIOS and have updated the charts below with the new results. [/EDIT]

There’s a huge difference between the two Gigabyte graphics cards. Nvidia’s reference board is almost exactly in the middle between them. The GTX 980 WindForce OC gives us our baseline by idling just under 10 W, while the derivative 970 consumes almost 20 W. This (relatively) massive difference was measured on the same platform using the same measurement methodology. Nvidia’s reference graphics card comes in at 16 W, right between the Gigabyte boards.

Our best guess is that Gigabyte has a “golden sample” at work here. But it goes to show what could be possible from Maxwell if production is refined further. We weren’t able to get our hands on a reference Nvidia GeForce GTX 970, so we had to use a downclocked version of a board partner’s card instead.

Gaming Power Consumption

These findings further illustrate what we said on the previous page about Maxwell and its ability to regulate GPU voltage faster and more precisely. The gaming-based power consumption numbers show just how much efficiency can be increased if the graphics card matches how much power is drawn to the actual load needed. The version of the GeForce GTX 980 that comes overclocked straight from the factory manages to use significantly less power than the reference version, while offering six percent more performance at the same time.

Let’s take a look at the measurements in detail. The large load fluctuations are plain to see.

Nvidia GeForce GTX 980 Reference Card Measurement Results and Graphs

Gigabyte GTX 980 WindForce OC Measurement Results and Graphs

Gigabyte GTX 970 WindForce OC Measurement Results and Graphs

Stress Test Power Consumption

If the load is held constant, then the lower power consumption measurements vanish immediately. There’s nothing for GPU Boost to adjust, since the highest possible voltage is needed continuously. Nvidia's stated TDP becomes a distant dream. In fact, if you compare the GeForce GTX 980’s power consumption to an overclocked GeForce GTX Titan Black, there really aren’t any differences between them. This is further evidence supporting our assertion that the new graphics card’s increased efficiency is largely attributable to better load adjustment and matching.

The values above have potential consequences for the everyday operation of these graphics cards, as they represent what can be expected when running performance-hungry compute-oriented applications optimized for CUDA and OpenCL.

That's not the only offering that makes a good impression, though. Nvidia's reference GeForce GTX 980 does well too, as long as you don’t focus on the idle power measurement. This isn't the same result as custom models with higher power targets (up to 300 Watts for the GTX 980), though, when compute-based stress tests are run. A taxing load just doesn't give Maxwell room for its optimizations to shine.

Note that the GeForce GTX 980's stress test power consumption is actually a few watts lower than the gaming result. This is likely due to throttling that kicks in when we hit the thermal ceiling.

Finally, let’s take a look at the detailed measurements. The much smaller load adjustments are illustrated graphically below. Pay particular attention to the reference card’s small drops when it hits the thermal limit.

Nvidia GeForce GTX 980 Reference Card Measurement Results and Graphs

Gigabyte GTX 980 WindForce OC Measurement Results and Graphs

Gigabyte GTX 970 WindForce OC Measurement Results and Graphs

Maxwell’s performance can almost be compared to that of a compression tool. Already compressed data (our compute-heavy numbers) can’t be compressed any further, whereas text (games) can be compressed massively.