The US Tom’s Hardware graphics lab continues utilizing 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. Sapphire's Pulse Radeon RX 5700 XT gets all of its power from the PCIe slot, one eight-pin auxiliary connector, and one six-pin connector.
Sapphire’s idle power consumption is just a hair higher than the AMD reference Radeon RX 5700 XT. Readings from the PCIe slot’s +12V rail are slightly elevated. The same goes for the eight-pin power connector. Meanwhile, the PCIe slot’s +3.3V rail and the six-pin auxiliary connector’s averages drop.
More aggressive clock rates compared to AMD’s reference Radeon RX 5700 XT result in slightly higher power consumption from Sapphire’s Pulse model. The difference isn’t huge, though—you’re looking at roughly 15W on average through our Metro benchmark sequence. The delta between our peak readings is even smaller.
More than half of what we see as an increase comes from the PCIe slot’s +12V rail. The rest is evenly divided between the auxiliary power connectors.
Illustrating power over time yields a handful of smooth lines across three runs of Metro, with a dip between each pass.
Sapphire’s Pulse Radeon RX 5700 XT is in red, while AMD’s reference Radeon RX 5700 XT is in black. Interestingly, the subtle difference between them is larger than comparing the AMD version to Nvidia’s GeForce RTX 2070 Super, a card that generally outperforms both Radeon RX 5700 XTs. Despite its utilization of GPUs manufactured at 12nm, Nvidia maintains an efficiency advantage over the 7nm Navi chips.
Sapphire wisely keeps current draw over the PCIe slot’s +12V rail to roughly 4A. That’s well below the PCI-SIG’s 5.5A ceiling.
Average power consumption increases slightly under FurMark compared to a gaming workload. However, the difference between Sapphire’s Pulse Radeon RX 5700 XT and AMD’s reference card remains 15W. Again, most of that is attributable to a >10W jump over the PCIe slot’s +12V rail.
Given Sapphire’s purported use of AMD's reference Radeon RX 5700 XT design, we’re not surprised to see the same sort of line chart under FurMark that we published in our Radeon RX 5700 XT launch coverage. At that time, AMD issued the following statement to us:
“The behavior you are seeing under a purely synthetic power virus (FurMark) workload is within our specified product parameters.
There are many different sensors and related algorithms that work to keep the GPU working within its prescribed product limits; the behavior depicted and described suggests that specific workload segments in FurMark are periodically causing a rapid ramp in temperature. When the algorithms respond, there is an intentional, designed-in delay which results in the observed ‘spike’.
The absolute values displayed are still within spec, showing that the electrical and thermal protection mechanisms built in to the RX 5700 series are working per design.”
We’ll see on the next page that Sapphire’s Performance BIOS maintains a clock rate advantage over AMD’s reference card, suggesting that the power measurements we see in FurMark aren’t negatively affecting frequency.
The Sapphire and AMD cards exhibit the same spiky power behavior under FurMark. This view also shows us the Pulse Radeon RX 5700 XT’s 15W-higher consumption compared to AMD’s reference Radeon RX 5700 XT.
Current draw over the PCIe slot’s +12V rail is slightly higher under FurMark than it was in Metro. But notice that our readings never spike up, whereas they do over both auxiliary power connectors.
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