on the evga or reference with a prior version to the bios i just mentioned they do...things change with each bios release though.
P1 and P2 options are there to force the option ON after the cut off point.

I have a feeling they are tied to tRD some how in a bid to increase FSB capability on the chipset, more testing will soon prove this right or wrong. I have 0507 for the Asus also which has tRD along with P1 and P2, thing is tRD does next to nothing unless you set 1 where it just stops the board booting.
Side note..tRD on the formula does nothing, its a placebo option as far as i know...set what you like to look good but don't expect a performance increase

i just got going on 790i, I did 8GB at 2000 on FCG's Asus rig which I have not seen anyone else do yet and now the quest is to get the XFX doing it also if I can get this bios to flash on monday