AMD Radeon RX Vega 56 8 GB 101

AMD Radeon RX Vega 56 8 GB Review

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Power Consumption

Improving power efficiency of the GPU architecture has been the key to success for current-generation GPUs. It is also the foundation for low noise levels because any power consumed will turn into heat that has to be moved away from the GPU by its thermal solution. An optimized fan profile is also one of the few things board vendors can create to impress with reference designs where they are prohibited from making changes to the thermal solution or components on the card.

For this test, we measure power consumption of only the graphics card via the PCI-Express power connector(s) and PCI-Express bus slot. A Keithley Integra 2700 digital multimeter with 6.5-digit resolution is used for all measurements. Again, these values only reflect the card's power consumption as measured at its DC inputs, not that of the whole system.

We use Metro: Last Light as a standard test for typical 3D gaming usage because it offers the following: very high power draw; high repeatability; is a current game that is supported on all cards; drivers are actively tested and optimized for it; supports all multi-GPU configurations; test runs in a relatively short time and renders a non-static scene with variable complexity.

Our results are based on the following tests:
  • Idle: Windows 10 sitting at the desktop (1920x1080) with all windows closed and drivers installed. The card is left to warm up in idle mode until power draw is stable.
  • Multi-monitor: Two monitors are connected to the tested card, and both use different display timings. Windows 10 is sitting at the desktop (1920x1080+1280x1024) with all windows closed and drivers installed. The card is left to warm up in idle mode until power draw is stable. When using two identical monitors with the same timings and resolution, power consumption will be lower. Our test represents the usage model of many productivity users who have one big screen and a small monitor on the side.
  • Blu-ray Playback: Power DVD 15 Ultra is used at a resolution of 1920x1080 to play back the Batman: The Dark Knight Blu-ray disc with GPU acceleration turned on. Measurements start around timecode 1:19, which has the highest data rates on the BD with up to 40 Mb/s. Playback keeps running until power draw converges to a stable value.
  • Average (Gaming): Metro: Last Light at 1920x1080 because it is representative of a typical gaming power draw. We report the average of all readings (12 per second) while the benchmark is rendering (no title/loading screen). In order to heat up the card, the benchmark is run once first, without measuring power consumption.
  • Peak (Gaming): Same test as Average, but we report the highest single reading during the test.
  • Sustained (Furmark): We use Furmark's Stability Test at 1600x900, 0xAA. This results in a very high no-game power-consumption reading that can typically only be reached with stress-testing applications. We report the highest single reading after a short startup period. Initial bursts during startup are not included as they are too short to be relevant.
Power consumption results of other cards on this page are measurements of the respective reference design.
Power consumption has been AMD's biggest problem area in recent years, especially when compared to the huge advances NVIDIA made here. RX Vega comes with an updated approach to power management, thanks to a beefed-up power-management microcontroller in the GPU die, which monitors and regulates all aspects of the board's power delivery and thermals.

Single-monitor idle power consumption seems surprisingly high, especially when considering that cards like the RX 580 managed to go below the 10 W mark, making them competitive with NVIDIA's designs which run single digit numbers in this test. One reason for this seems to be the relatively high idle GPU clock of 852 MHz, while memory goes down all the way to 167 MHz.

Multi-monitor power consumption seems solved, finally. With 16 W, the power increase over single-monitor idle is just 2 W, a huge improvement over the 15 W or so that were previously added in that state (on Polaris); the same goes for media playback.

We saw very high power consumption in today's other review of the RX Vega 64. The RX Vega 56 does a lot better; the difference is almost magical. With 229 W, power draw is 30% better than with RX Vega 64, at the cost of 10% performance, resulting in greatly improved performance per watt. With those numbers, Vega efficiency competes with some Pascal cards - these are the numbers I was hoping for with Vega.

It seems that RX Vega 56 runs much closer to the optimal voltage/frequency curve than RX Vega 64, which seems to have been clocked very high just to match GTX 1080 performance. Each chip design has an optimum efficiency operating point that delivers a certain performance; if you want higher performance, you have to sacrifice some efficiency to drive the GPU hard enough to achieve your goals.

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