Thought I'd share some info.
It's considered old info now.
Been testing during the pre-launch phase with beta(buggy) bios and what not.
Haven't had the time to update except inform some dealers.
For rams on the 3000 series.
Now pretty much almost any tom dick harry rams will work.
Of course if you want assurance, then go for the amd qvl ones which more options will be available soon.
3200 is pretty much out of the box. (16-32GB set ups)
3600MHz is the sweet spot.
After that, the infinity fabric breaks into a 2:1 ratio.
(read the info online, I had no idea then)
With higher density modules, you will pretty much see a visible boost in performance.
ie.16GB modules.
I tested with a variety of rams.
8GB x2/x4
16GB x2/x4
As of after the launch, vendors have been churning out bios every few days.
(Even for x570)
So bear with it for the time being.
Some of the common occurrence that you may face,
black screen with blinking activity light after the flash.
Just power down, clear the cmos and boot again after awhile, it should work.
Failed mem oc, clearing cmos may take forever.
Just pull out the rams and boot with a different stick.
It will generally recover straight away.
64GB works like a charm even on the B450 now.
Tested with the most basic G.skill Ripjaws V 2666C15 32GBkits x 2.
Sniper X 3200 16x2x2 and 3600 8x2 as well.
Mixed modules tested @ well.
3800MHz on the B450
IF ram ratio becomes 2:1
Although compatibility is awesome now,
there isnt much difference in performance(cas latency wise as well).
So 64GB, 3200MHz is the dope spot.
3600 is pretty much the sweet spot if u have a decent kit before.