Soldato
So only just noticed that Gigabyte have the x99 fixes (dated the 11th), so been there for a while.
My board
https://www.gigabyte.com/Motherboard/GA-X99-SLI-rev-10#support-dl
F24a 6.66 MB 2018/01/11 1. Update CPU Microcode
Judging by the date, I assume it's the bugged code that was causing reboots? that Intel are fixing, so I should wait? Or was haswell-e safe from that?
There's a bios update for the Gaming 5P too, but like you, I'm hesitant to install it because of the reported reboot issues from these quick fixes that appear to have by-passed QC.