Well, as I say, the chipset supports 1333 FSB, but it certainly was the case when the boards were new, that they needed flashing, as is the case with yours...
Hrm.. the eVGA mobo mentioned needs bios version P29 or later, and I have no idea whether the manufacturers keep churning out the originals, and just upload the new bioses online, or whether they come updated. Presumably they need to put a BIOS of some description on, and hence would use the most recent, but then you are gambling on how new the stock is when you buy...
I haven't found any hard answer from searching online since my last post, I'm afraid..
sorry!
mgcook uses an eVGA NF680, he might know!
(oh and both yours and the eVGA are great boards)
p.s. I didn't mean to imply that the P35 is the only 1333FSB chipset, I just mean that I think you wont need to flash them