Flash a Radeon HD 4870 with Mac OS X

A recent trick we described generated a lot of interest among Mac Pro owners (all generations included): flashing a PC Radeon HD 48x0 to work in a Mac. So, far the procedure (partially described here), required CD Freedos to access Atiflash tool.
Thanks to Apple and the recent firmware update of some Radeon installed in iMac, we obtain a Mac version of Atiflash. The procedure is available already in English (we will not comment it further before having it fully tested): http://boeglin.org/blog/index.php?entry=entry090918-031702 

In summary, it requires the firmware update of an iMac, Pacifist to extract archive, firmware dedicated to HD 4870/4890 and a couple of command lines to enter in the Terminal. We currently do not know if it will work for all PC Radeon HD 48x0 cards, and particularly on all EEPROM.
Last but not least, one will of course need a second graphic card to keep having all information displayed on your monitor during the flashing procedure.