I read your message and boot log on the web archives, so I can reply.
Copying you direct so we can connect directly - I'm (also) only
subscribed to a daily digest.
So you can indeed use an unmodified asus/p2b build. Perfect. Going
forward you can act as if you have a p2b. We'll note elsewhere this
mainboard can also support a p2-99.
Your boot log does indicate the same missing MBRS error I got. Now I
know what I need to do next.
The early CBMEM init patch is here: https://review.coreboot.org/c/22228/
Apply it to a clean p2b build, config for a spew debug level, and see
if you can capture a log over serial. Also try the two cbmem commands
Paul provided in the patch and see what you get.
Looking forward to your results.