Actually it's not. With the switch to Intel processors, Apple also moved from Open Firmware to EFI, which is an updated BIOS specification developed by Intel. Advanced features include the ability to boot into an EFI shell and run diagnostics and power up the CPU into a fully functional state immediately.

EFI also separates the control of devices from the operating system, meaning it can initialize hardware before loading the OS. This feature would allow for a system to connect to the Internet and download updated drivers before booting up.

Intel initially deployed EFI as part of its Itanium architecture. As such, Microsoft only included support for the BIOS replacement in its IA64 and later x64 operating systems. While Microsoft plans to add EFI support in 32-bit versions of Windows Vista, a final release isn't due until the end of the year.

Microsoft's 64-bit versions of Windows will also not work despite supporting EFI, because Apple's Intel platform is strictly 32-bit at the moment. It would be nice, but right now it's not possible.