Our stock setups for both AMD and Intel processors use the vendor-specified stock memory frequency. We tested the overclocked -9900K/S models at DDR4-3600 to highlight the performance advantages of memory tuning.
Test results annotated with "PBO" reflect performance with AMD's auto-overclocking Precision Boost Overdrive feature activated. Those configurations also run at DDR4-3600.
VRMark and 3DMark
We aren't big fans of using synthetic benchmarks to measure performance, but 3DMark's DX11 and DX12 CPU tests provide useful insight into the amount of horsepower available to game engines.
As expected, the Ryzen 9 3900X takes a commanding lead during these benchmarks, largely because the tests scale well with extra threads. The overclocked Core i9-9900KS does come close to matching AMD's flagship, but falls short.
The -9900KS redeems itself in VRMark, which favors per-core performance. The Ryzen 9 3900X falls to the bottom of the chart, while the tuned Ryzen 7 3700X beats the stock -9900K.
Civilization VI AI and Stockfish
Stockfish, an open-source chess engine, is the perennial world leader in computer chess competitions, beating other engines like Google's Deepmind AlphaZero. The engine is designed to extract the utmost performance from many-core chips, so it scales well up to 512 cores. That parallelism hands the 24-thread Ryzen 9 3900X a convincing win.
Civilization VI's AI performance test is highly dependent on per-core performance, which plays well to the Core i9-9900KS's strengths as it takes the uncontested lead. We tuned the overclocked Core i9-9900K configuration with DDR4-3600 memory, while the stock -9900KS operates at its standard DDR4-2666. The KS still manages to pull off the win against its counterpart.
Ashes of the Singularity: Escalation
The stock Core i9-9900KS matches the overclocked -9900K step for step, while tuning both the chip's cores and memory allows it to take a decent lead over the fully-overclocked -9900K, not to mention the overclocked Ryzen 9 3900X.
At stock settings, however, the -9900KS's advantage over the stock -9900K is slight.