Will the AM3+ Sabertooth 990FX support RAM up to 2133mhz despite the fact the ASUS website description only mentioned 1866mhz?

Some RAM brands should make it to 2133mhz. And heck, if you configure it manually (timings included) you should be able to get there.

I think your best bet is Corsair Vengeance RAM.

yes you can overclock the ram manualy thats no problem, but you will be absolutly fine with 1866mhz ram. i dont see the bennefit of buying much more expensive 2133mhz or even 2400 mhz ram,  i would personaly prefer 1866mhz with low cas latancy.

I know the software suite is still a pile of steaming crap except the wifi go program . I really prefer bios .

I say that and it just gave me a auto tune of 4552.2 at 1.413 volts :)

I run 32gb's of 2133 mhz ram in mine with no problem

I had to alter the timing manualy slightly though and that was it.

It'll support it but i think your system will downclock it to 1866mhz.

I am pretty sure just flip it to manual and set it to 2133.

 

yep

11,12,11,33 at 1.6v

supposed to be 32 but wasnt stable unless I upped the voltage to 1.65 (which i wasnt happy with)

I was going to up mine to 16g once i started crossfiring. So maybe no issue ? Running 8 gigs of gskills with  10 12 12 31