You're definitely correct, I found
this AM3 VRM spreadsheet which I had previously looked over because I was focused on
the AM3+ list, and it confirms it's an 8+1 phase. Also, confirms that the M4A89GTD Pro/USB3 is 8+2
Source w/ other sockets too
I didn't know that about the Sabertooth revisions, thank you for sharing.
A word of caution if you didn't already know: MSI usually had terrible VRMs from the 700-900 ATI/AMD chipset series (until late in the 900 life cycle), they were poorly engineered and I personally experienced a VRM failure out of the blue years ago using an FX-8350 on a 970A-G43 (not overclocked). The 890FXA GD70 suffers from some VRM issues as well, mainly no VRM thermal throttling/shutdown and some failures with overclocking Phenom II 6-core parts (and presumably, 6/8c FX parts). This is not to degrade your purchase whatsoever, just advice, I would rather you not break such a pretty board or any valuable CPU. And it's not that bad, you can definitely OC, you just gotta point a fan at the VRM and make sure it's not going over 100°C and that's fixed
The links I gave above to
@lexluthermiester have spreadsheets with all brands' boards of a given socket, in case you would like to read up. For convenience
here's MSI.