A full mitigation could be applied, eliminating any possibility of the issue affecting a Mac, but in the process it disabled hyper-threading and, by Apple's estimates, reduce system performance by as much as 40%. This reduction only applied to anyone who enabled the full mitigation in the Mojave update, as well as those who installed Security Update 2019-003 for High Sierra and Sierra and similarly enabled it.Windows users are also affected, but Microsoft doesn't recommend the disabling of Hyper-Threading due to the big performance impact. Basically, all these CPU vulnerabilities are a giant mess and it will take a couple more years until this is all patched on the hardware-level. This type of security has been neglected for too long, and now Intel and its users are bearing the brunt.
This potential loss of performance immediately caused uproar from concerned users, though the anger is overblown, and not specific to the Mac.
Apple: Up to 40 percent reduction in performance due to Intel MDS issues
Posted on Friday, May 17 2019 @ 10:38 CEST by Thomas De Maesschalck