I'm on 7C37vH6
Just having a play with things at the moment, I don't think that MSI's stupid Dragon software was helping as that did it's own thing to the clocks every time it loaded so I've uninstalled it.
I reset BIOS back to default and it was still only running at 3.8. Then I've loaded Ryzen Master and it's noted as being a Manual OC (which is isn't on bios default settings!) so I reset Master too and... it now seems to be boosting to 4.6 single core.
I miss the old days of bclk overclocking, this is getting far too complicated for me!
