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Power Consumption
Slowly but surely, we’re spinning up multiple Tom’s Hardware labs with Cybenetics’ Powenetics hardware/software solution for accurately measuring power consumption.
Powenetics, In Depth
For a closer look at our U.S. lab’s power consumption measurement platform, check out Powenetics: A Better Way To Measure Power Draw for CPUs, GPUs & Storage.
In brief, Powenetics utilizes Tinkerforge Master Bricks, to which Voltage/Current bricklets are attached. The bricklets are installed between the load and power supply, and they monitor consumption through each of the modified PSU’s auxiliary power connectors and through the PCIe slot by way of a PCIe riser. Custom software logs the readings, allowing us to dial in a sampling rate, pull that data into Excel, and very accurately chart everything from average power across a benchmark run to instantaneous spikes.
The software is set up to log the power consumption of graphics cards, storage devices, and CPUs. However, we’re only using the bricklets relevant to graphics card testing. AMD's Radeon VII gets all of its power from the PCIe slot and a pair of eight-pin PCIe connectors. Should third-party Vega 20-based board materialize at some point in the future with three auxiliary power connectors, we can support them, too.
Gaming: Metro: Last Light
Three runs of the Metro: Last Light benchmark give us consistent, repeatable results, which makes it easier to compare the power consumption of graphics cards.
AMD extracts as much performance out of Radeon VII's power budget as possible. Through our three-run recording, the card averages almost 298W with spikes that approach 322W.
Very little power is delivered over the PCI Express slot. Rather, it's fairly evenly balanced between both eight-pin auxiliary connectors.
The blue overall power consumption line, representing the sum of all other lines, mostly obeys AMD's 300W limit.
Less impressive is the fact that Radeon VII does battle against a card rated for 75W less, manufactured on a 12nm node. Even GeForce RTX 2080 Ti, which is significantly faster, uses quite a bit less power.
At least AMD isn't in unprecedented territory. Despite a supposed 295W power limit, its Radeon RX Vega 64 demonstrated a similar power profile as Radeon VII.
Current over the PCIe slot stays just over 2A. Clearly, those eight-pin connectors do most of the heavy lifting here.
FurMark
FurMark is a steadier workload, resulting in less variation across our test run. Average power does rise slightly to 309W with spikes as high as 330W.
The much more consistent workload makes it easier to compare draw over each rail. Again, AMD achieves good balance between its two eight-pin auxiliary connectors, while the PCIe slot averages 30W.
GeForce RTX 2080 and 2080 Ti are well-behaved. They operate within a tight power range and generally obey Nvidia's limits.
Radeon RX Vega 64 has a harder time keeping up with the demands of FurMark. It starts off strong, quickly heats up, and then oscillates within a ~15W range to avoid violating one of AMD's upper bounds.
Radeon VII doesn't have the same issue. Its power consumption line chart isn't as tightly grouped. But the card still maintains its performance under that full-length heat sink and trio of axial fans.
Current draw over the PCIe slot hovers between 2A and 3A, leaving lots of headroom under the 5.5A ceiling.
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