I have a related issue in that I have been planning on utilizing an Opteron 175 in a A8N-SLI Premium motherboard. While the 175 is not officially supported, there appears to be multiple individuals using this processor in this motherboard successfully.
I have read in a review (newegg?) that someone with a X2 4800 was not able to boot on this motherboard and believed the problem was that the bios needed to be updated to boot the 4800 (which required a different processor supported by the lower versioned bios originally supplied on the motherboard).
The question I have, related to the x2, is will the bios which comes with a (to be purchased) A8N-SLI Premium motherboard boot (perhaps in single-processor) an Operon 175 ?