New World ROM

New World ROM Macintosh computers are the models that do not use a Macintosh Toolbox ROM on the logic board, but instead use an Open Firmware boot ROM. All Macs from the iMac G3 onward are New World ROM machines, while all previous models are Old World ROM machines. PCI-based "beige" Power Macintosh models use a combination of Open Firmware with an Old World version of the Macintosh Toolbox included in the ROM as an Open Firmware device.

When booting into classic Mac OS on New World models, the Toolbox is instead loaded into RAM from a Mac OS ROM file in the boot volume's System Folder. In Mac OS X, this Toolbox ROM file is not used except when running the Classic environment.

New World ROM Macs can boot into Mac OS X directly, since Open Firmware allows precise designation of the startup files. Non-Mac operating systems, such as BSD variants and Linux can also boot directly using the same mechanism.

Intel-based Mac computers are incapable of natively running Mac OS 9 or the Classic environment. EFI is used on these machines instead of Open Firmware.