Core i9-9900KS Power Consumption
We recently migrated to a more efficiency-focused approach to quantifying power consumption, but measurements can be tricky. We ensure that our 12V supply (EPS) readings, motherboard power supply sensor values, and voltage transformer losses plausibly coincide with external measurements generated with our Powenetics test gear. After verification, we use pure package power measurements to avoid possible influences from our motherboard. Results from the PWM controller are very reliable if you take them as averages over a few minutes.
We began our power testing with the AIDA 64 stress test with AVX enabled. The stock -9900KS draws 7W of additional power over the Ryzen 9 3900X. After overclocking, that gap widens to 17W, but it is important to remember that AMD's auto-overlocking precision boost overdrive feature (PBO) doesn't impart very large performance gains in most workloads. However, the feature does get us within range of the 3900X's maximum overclock ceiling.
The -9900KS only draws 12W more than the stock -9900K during the AVX test, but runs at 5.0 GHz on all cores. Meanwhile, the -9900K downshifts to 4.7 GHz under the AVX load. The KS also draws 20W less than the vanilla model after overclocking but gains an extra 200 MHz of clock speed. We see much of the same trend during the AIDA 64 non-AVX test.
Peak stock power draw for the -9900KS weighs in at 158W during the y-cruncher benchmark, which computes pi using a heavily-threaded AVX workload. That falls neatly in line with Intel's PL2 value (although the chip certainly boosts longer than the 28-second Tau guideline). The stock Core i9-9900KS stays under 150W during our AVX-enabled HandBrake x264 and x265 tests, that latter of which uses a heavier distribution of the densely-packed SIMD instructions.
The -9900KS consumes far less power at its stock 5.0 GHz than we need to push the -9900K to similar levels of performance, a delta that meets or exceeds 50W in some workloads. That equates to less waste heat dumping into your case and also helps explain the additional overclocking headroom.
Even though both processors are operating at 5.0 GHz on all cores, the stock Core i9-9900KS is much more efficient than the overclocked Core i9-9900K during our round of performance benchmarks. However, the Ryzen 9 3900X's hefty allotment of 12 cores and 24 threads easily provides more performance than Intel's eight-core -9900 models.