huge performance hit with ucode c6 on 806eb and 906e9 after inserting those can be observed in win 1903 and 1909 across different benches. For example cinebench 15 , - 30-40 points on 806eb.
Ucodes tested with vmware software.
Went back to b8 on 806eb and b4 on 906e9 everything back to normal scores.
From my testings so far best ucodes are AE for both or b8 for 806eb and b4 for 906e9. Latest two gave slightly better scores than AE
Need to test BA for both but I didn’t have time to check and download and it wasreplaced by c6 so if someone could upload BA for 806eb and 906e9?
Can confirm. 906EC (whatever the 9900K one is) with version C6, loses over 1 multiplier worth of Cinebench R15 and R20 benchmarks (dropping the 5.1 ghz scores to lower than the 5 ghz scores on previous BE microcode).
Complete garbage. 
And this performance hit happens even on an OS which is not mitigation aware at all (1703), so no mitigations are even installed.
You can test microcodes without putting them into your modded Bioses by unpacking the old VMware program into a folder, deleting "Microcode.dat" (as it’s old old old), putting the new microcodes into a temp folder, then running the converter on them to convert them into a new microcode.dat. Then "install.bat" them as administrator. Uninstall them with the batch file if they’re garbage.
Intel Microcode.dat Converter.zip (7.37 KB)
Microcode_vmware.zip (3.47 MB)
@Falkentyne
Calm down, u seem very excited, not good for your heart health!!!
Intel wants u to buy its next cpu’s, they are safer and faster. A win win!!!
Can you please share the b4 for 906e9?
There is a method of installing a microcode update via a flash drive when the Pc boots which is as close to having it installed in the Bios as is possible without having to install windoze updates. I have not checked whether the registry patch really fully disables the microcode update inside windows. Inspectre is supposed to enable/disable the update after the windows update has been installed.
https://www.ngohq.com/intel-microcode-boot-loader.html