Source : http://club.tgfcer.com/thread-6596213-2-1.html
User "BD" was a former UBI (now other 3rd party) employee and says that he will leak infos about the 720's dedicated OS Ram, if MS will not spill the beans itself on E3.
Other users confirm his affiliation to the industry. This was done in course of a thread about the CVG 720 article we all know.
Now user " 战神blog", an alleged other insider, pretty much leaks the current (devkit?) specs:
and later as an answer on the question whether an 8800 or 8900 series GPU is used:
Eight-core cpu, 8g memory, 8xxx graphics, windows 8 kernel specially os, 640g hard drive.
(the 8880 seems to be a typo - I think he means 8800)
now "BD" comes back into the play and indirectly confirms this specs:
Disclaimer : everything was translated via google translate.
You're gone, I said you divulge sensitive information sent letters to the MS PR tomorrow.
Someone here speaking chinese and can confirm that I didn't misunderstand anything here?
Edit: it's AMD's 8800 series that is mentioned here. No idea whether 8850 or 8870. Most probably custom silicon in the final unit.