We establish the package’s power consumption results by using a special sensor loop. This way, our values represent the exact amount of power that goes into the CPU and then reemerges in the form of waste heat dissipated by the cooling subsystem. We check our sensor readings using shunts and by measuring overall power consumption directly at the EPS connector (with a current probe and direct voltage measurement).
AMD’s Threadripper CPUs use different partial voltages for the SoC and SMU rails at different clock rates. These partial voltages, which, again, vary based on frequency, do influence the package’s power consumption. AMD recommended that we use the profile included with its DDR4-3200 kit. But if we instead use the standard SPD values for DDR4-2133, our power measurement is 15W lower!Both of AMD’s CPUs are designed for a maximum power ceiling of 180W at their default settings. If the memory gets overclocked, the CPU has 15 fewer watts to work with. This could affect performance in workloads that utilize all cores and, consequently, get too close to the limit.
Idle Power Consumption
Threadripper’s idle power consumption is roughly twice that of the Ryzen 7 models. However, Threadripper also hosts two dies instead of one, and it also hits higher clock rates under sporadic loads. The overclocked version requires higher voltages as well, and memory also plays a role in power consumption. For instance, dropping to DDR4-2133 pulls the 1920X's idle power use down to 32W.
CAD Workload Power Consumption
AutoCAD 2016 rarely uses more than two or three cores. In fact, most of the time it's limited to a single core. Thus, it's not surprising that the CAD power consumption only adds a maximum of 15W to the idle power numbers. The two overclocked configurations add another 14W, which makes for an almost 30W difference compared to our idle power consumption results.
Gaming Power Consumption
When it comes to gaming, Threadripper’s MCM design causes its many cores to get in each others' way. Thus, the frame rates we report end up lower than competing processors. But power consumption ends up similar to Intel's Core i9-7900X, even though Skylake-X offers much more performance.
Stress Test & Maximum Power Consumption
Power consumption goes through the roof during our stress test, especially for the overclocked configurations.
The motherboard is partially to blame for the stock Intel Core i9-7900X's excessively high numbers. It doesn’t obey the standard Turbo Boost frequency thresholds, instead boosting aggressively and staying in those boost states longer than required. For more details, see our article about the power and thermal issues we encountered during our extended testing.
Threadripper doesn’t have those kinds of issues. Asus X399 ROG Zenith Extreme limits power consumption to exactly 180W at stock settings, just as it should.
At a respectable 1.425V, the Ryzen Threadripper 1920X reaches 4.1 GHz. The higher-end 1950X needs 1.35V to achieve 3.9 GHz. Once overclocked, AMD’s new processors join Intel's Core i9-7900X overclocked to 4.5 GHz in the stratosphere beyond 300W.
In the end, Threadripper's two dies sometimes consume more power than other processors’ single dies, depending on the task. We succeeded in breaking the 4 GHz barrier by overclocking the 1920X to 4.1 GHz. At that speed, all 24 threads were fully functional and at our disposal. The high power consumption is acceptable if it's accompanied by comparably elevated application performance. For Threadripper, that requires highly parallelized workloads (and perhaps optimized software).
Unfortunately, Threadripper's efficiency during gaming turns out to be significantly worse than Intel’s. Threadripper draws an additional ~15W at idle due to the memory. Subtracting that 15W from AMD's gaming power consumption changes the picture, bringing power consumption in line with the lower gaming performance.
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