Intel Core i5 8400 vs. i5 9400F Meltdown/Spectre/L1TF/MDS Mitigation Impact

With recently seeing a deal on the Intel Core i5 9400F processor, I picked it up for testing as part of our Spectre / Meltdown / Foreshadow / Zombieload testing since it features some hardware mitigations and is otherwise quite similar to the unmitigated Core i5 8400 that I also have in the benchmarking farm. Here are some results when benchmarking the Core i5 8400 and Core i5 9400F with and without the current Linux mitigations for these CPU vulnerabilities.

I'll have up my complete Linux review of the Intel Core i5 9400F over the next week or so, but given the interest in the mitigated performance especially after the last round (MDS / Zombieload), here are some metrics comparing just the Core i5 8400 and Core i5 9400F with their mitigations. The Core i5 9400 series is part of the line-up now featuring silicon-level mitigations for Meltdown and hardware/software improvements around Spectre and L1TF. Given the Core i5 8400 is quite similar but without any hardware mitigations, I figured it would be interesting for a benchmark candidate.

The F on the Core i5 9400F denotes this processor doesn't have any onboard graphics. The other differences between the i5-8400 and i5-9400F just come down to the 8400 model having a 2.8GHz base clock and 4.0GHz turbo clock while the i5-9400F has a 2.9GHz base clock with 4.1GHz turbo clock. So there's a 100MHz bump at the base and turbo frequencies and some level of new hardware protections built-in (and no graphics on the 9400F model) but the rest is the same with having six physical cores, no Hyper Threading, 9MB cache, and a 65 Watt TDP.

Both Coffeelake processors were benchmarked on an MSI B360M GAMING PLUS motherboard, 2 x 8GB Corsair DDR4-3200 memory, and 256GB Samsung MZVPW256HEGL NVMe solid-state drive. The system was running Ubuntu 19.04 with its updates Linux 5.0 kernel that does contain all the latest mitigations through MDS/Zombieload. Benchmarks were done on each processor when booted in the "mitigations=off" and mitigations=auto" state for seeing the impact of the default mitigations against the unmitigated state for these Core i5 Coffeelake CPUs. Neither CPU has Hyper Threading and obviously all six physical cores were enabled.

Here's a look at how the performance compares under a variety of mitigated-prone workloads measured via the Phoronix Test Suite.