G.Skill 4266 only boots as 2133, before it was working as DDR3600 with 1800Bus/IF clock since the beginning - opened already another thread for this issue/board. I even had to start from scratch with my settings, as all of my profiles set lots of values to nonsense (SATA, LAN, Audio, USB3 all to off, VRM switching frequency 15200, ProcOdt to high impedance ...) - all previous Bios version had no issue when loading one of these profiles.
Now it's turning on with fans running, but it isn't showing Bios screen anymore and the TUF X570 has no CMOS clear button and it is hard to access the jumper in my setup ... That's the biggest b.....t I've ever had since I own PCs, and with 50+ this is a long time!
With my setup I tried to set all the values manually for 3600/1800 and it still didn't work. What I did find kinda work was to set everything for 3200 and then set it to 3600. However after a cold boot it would also fail.
I might try again, but in the meantime I used the flashback button to go back to a previous bios.
So I got my TUF working again after CMOS Reset ...
Used Overclocking Auto instead DOCP (not sure why Auto allows settings of Frequency but anyway - CPU-Z showed correct values) and setting DDR 3600 with FCLK 1800Mhz, 15/15/15/15. Voltage at 1.35V, IF 1800MHz ... and it worked for the last 2 hours, playing games only.
*The only thing is that secondary and third timings are far to high, but for now it's ok and I hope they get the XMP Profile working again, so that I get the better timings automatically.*