

Apple also starting including logic board firmware updates with the other updates downloaded to your Mac. These modifications brought the method closer to the UEFI standard. Meanwhile, Microsoft modified their method for booting windows installers from flash drives. Apple decided not to issue firmware updates for the older Mac that had internal DVD drives. The necessary changes were made to the firmware on these Macs to allow Windows to be installed from USB flash drives. Starting in the 2012 model year, Apple started producing Macs without internal DVD drives. This DVD method of installation was the only way to install Windows through the release of Windows 7. There was no option to use a USB flash drive installer. So to install Windows, you need a XP installation DVD with Service Pack 2 already installed.

Apple offered firmware downloads up update the logic boards. Microsoft put the necessary changes in Service Pack 2 for the XP operating system. When Apple decide to allow Windows installation Macs, Microsoft needed to change its software and Apple had to change the firmware in the Mac logic boards. I will try a simple answer followed by a more complex answer.
