It really sucks that Asus don't update their BIOS to the X99 platform
... or EVGA for that matter.
MSI wrote to me that the new Intel
Microcode was implemented into all X99 BIOS versions from June 2018, so users shouldn't experience any issues.
I checked some Gigabyte board and it
is not all boards that have a new Intel microcode BIOS update available.
Heres a handfull of Gigabyte boards that I checked have the latest Intel microcode BIOS update to download.
GA-X99P-SLI
GA-X99-SOC Champion
GA-X99-UD3
GA-X99M-Gaming 5
GA-X99-Designare EX
GA-X99-Ultra Gaming
GA-X99-UD4P
GA-X99-SLI
GA-X99-Phoenix SLI
GA-X99-UD5 WIFI
As for ASRock
all X99 boards should have updated Intel microcodes ready for download. These boards I have checked have new BIOS microcode updates.
X99 Extreme3
X99 Extreme4
X99 Extreme6
X99 WS
X99 OC Formula/3.1
X99 Taichi
Fatal1ty X99 Professional/3.1
X99 Extreme11
Fatal1ty X99M Killer
Fatal1ty X99X Killer