Old World ROM Macintosh computers are the Macintosh models that use a Macintosh Toolbox ROM chip, usually in a socket (but soldered to the motherboard in some models). All Macs prior to the iMac use Old World ROM, while the iMac and all subsequent models are New World ROM machines. In common use, the "Old World" designation usually applies to the first generation of PCI-based Power Macs (and sometimes the very first NuBus-equipped models), but not the older Motorola 68000-based Macs; however, the Toolbox runs the same way on all three types of machines.