Hi The Rominator!
Here it is
Okey doke there sport.
And keep in mind, the actual wizardry behind this is Netkas' who cobbled together the EFI from an iMac EFI. So, if anything goes wrong...BLAME HIM !!!!
Seriously, I think this is right but as we are at the very forefront of 5870 modding/flashing, who knows?
But this absolutely should function exactly as before in Windows.
Be sure that you have installed the ATI parts of "iMac Mid 2010 10.6.4 update" or the "Snow Leopard Graphics Update".
Keep in mind that you will NOT see anything on display until desktop pops up.
It may be possible to use some combo of matching displays to properly trigger EDID to get boot screens, I will try this out soon.
Please post results.
I hope that you have access to an actual PC in case this buggers up your card.
Good luck !!! You will have 2nd flashed & working Mac 5870 if it works out !!!