New
#70
Thanks for the link, quote:
At boot up the appropriate microcode data is copied to the CPU at boot time, but only if the revision stored in this file is later than the revision that was copied to the CPU by the bios prior to boot. So anyone who gets a bios update with the new microcode from their OEM/supplier, won't see any affect of this update.
Some correction for this quote from the link...
The OS will copy the newer microcode code to the CPU during boot time. Once the system is shutdown, the copied microcode stays in the OS partition, but not in the CPU in itself. If the system only has Windows OS, loosing the copied microcode in the CPU does not matter. Windows just copies the microcode again at the next time the system is booted.
If the system is dual booted and neither the BIOS nor the second OS have the latest microcode, the second OS is vulnerable to the Meltdown/Spectre exploits.
There's some disadvantage for manually applying the KB4090007. If the backup image restored does not have this patch installed, it will be vulnerable until it is installed, provided the BIOS had not been updated with the latest microcode. The same goes for reinstalling Windows, since the KB4090007 is not pushed to Windows by MS.
If the motherboard has been updated with the latest microcode, it does not matter if the KB4090007 had been installed manually, or not. Windows, for that matter Linux, will not overwrite the microcode, if and when the BIOS has the same or later version of the microcode.