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, the iBook, the Blue and White Power Mac G3 and the Bronze Keyboard PowerBook G3 use Old World ROM, while the iMac, iBook, Blue and White G3, and Bronze Keyboard PowerBook G3, as well as all subsequent models until the introduction of the Intel-based EFI Models are New World ROM machines. In particular, the Beige Power Mac G3 and all other beige and platinum colored Power Macs are Old World ROM machines. In common use, the "Old World" designation usually applies to the early generations of PCI-based "beige" 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.

L'Old World ROM est un composant de mémoire ROM des modèles Macintosh utilisant une boîte à outils Macintosh, le plus souvent sur une douille. À partir de l'iMac c'est la New World ROM qui est en fonction. Pour les Macs plus anciens basés sur le Motorola 68000 le démarrage commence directement sur ladite boîte à outil.