The combined mitigations for Spectre, Meltdown, L1TF, MDS, and Zombieload have decreased the performance of Intel’s CPUs substantially. Phoronix’s Michael Larabel ran tests on the 6800K (Broadwell-E), 8700K (Coffee Lake), and 7980XE (Skylake-SP) with default mitigations applied and found a performance decrease of around 16 percent. With Hyper-Threading disabled, that figure becomes 20 percent, 24.8 percent, and 20.5 percent, respectively.
Larabel also tested two AMD parts, the Ryzen 7 2700X and Threadripper 2990WX. These chips only saw a performance loss of 3 percent.
If looking at the geometric mean for the tests run today, the Intel systems all saw about 16% lower performance out-of-the-box now with these default mitigations and obviously even lower if disabling Hyper Threading for maximum security. The two AMD systems tested saw a 3% performance hit with the default mitigations. While there are minor differences between the systems to consider, the mitigation impact is enough to draw the Core i7 8700K much closer to the Ryzen 7 2700X and the Core i9 7980XE to the Threadripper 2990WX.