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New World ROM computers areMacintosh models that do not use aMacintosh ToolboxROM on the logic board.[1] Due toMac OS X not requiring the availability of the Toolbox, this allowed ROM sizes to shrink dramatically (typically from4 MB to1 MB), and facilitated the use offlash memory for system firmware instead of the now more expensive and less flexibleMask ROM that most previous Macs used. A facility for loading the Toolbox from the startup device was, however, made available, allowing the use ofMac OS 8 andMac OS 9 on New World machines.
The New World architecture was developed for theMacintosh Network Computer, an unrealized project that eventually contributed several key technologies to the first-generation iMac.
AllPowerPC Macs from theiMac, theiBook, theBlue and White Power Mac G3 and theBronze Keyboard (Lombard) PowerBook G3 forward are New World ROM machines, while all previous PowerPC models (including all PCI-based Power Macs such as the Beige/Platinum Power Mac G3 and some NuBus-based Power Macs) areOld World ROM machines.Intel based Macs are incapable of running Mac OS 9 (or, indeed, any version of Mac OS X prior toTiger), and on these machinesUEFI is used instead ofOpen Firmware, which both New World and Old World machines are based on.
New World ROM Macs are the first Macs where direct usage of theOpen Firmware (OF) subsystem is encouraged. PreviousPCIPower Macs used Open Firmware for booting, but the implementation was not complete; in these machines OF was only expected to probe PCI devices, then immediately hand control over to the Mac OS ROM. Because of this, versions 1.0.5 and 2.x had several serious bugs, as well as missing functionality (such as being able to load files from aHFS partition or aTFTP server). Apple also set the default input and output devices tottya (the modem port on beige Macs), which made it difficult for normal users to get to Open Firmware; to do so it was necessary to either hook up a terminal, or change the Open Firmware settings from inside Mac OS using a tool such asBoot Variables or Apple'sSystem Disk.
The New World ROM introduced a much-improved version of the Open Firmware interpreter, version 3.0, which added many missing features, fixed most of the bugs from earlier versions, and had the capability to runCHRPboot scripts. The Toolbox ROM was embedded inside a CHRP script in theSystem Folder called "Mac OS ROM", along with a short loader stub and a copy of theHappy Mac icon suitable for display from Open Firmware. Once the ROM was loaded from disk, the Mac boot sequence continued as usual. As before, Open Firmware could also run a binaryboot loader, and version 3.0 added support forELF objects as well as theXCOFF files versions 1.0.5 and 2.0 supported. Also, version 3.0 (as well as some of the last releases of version 2.x, starting with thePowerBook 3400) officially supported direct access to the Open Firmware command prompt from the console (by setting theauto-boot? variable tofalse from Mac OS, or by holding down⌘ Command-⌥ Option-O-F at boot).
One major difference between Old World ROM Macs and New World ROM Macs, at least in Classic Mac OS, is that the Gestalt selector for the machine type is no longer usable; all New World ROM Macs use the same mach ID, 406 decimal, and the actual machine ID is encoded in the "model" and "compatible" properties of the root node of the Open Firmware device tree. The New World ROM also sets the "compatible" property of the root node to "MacRISC2" (machines that can boot Classic Mac OS using "Mac OS ROM") or "MacRISC3" (machines that can only bootMac OS X or anotherUnix-like system).
It is somewhat easier to boot a non-Mac-OS operating system on a New World system, and indeedOpenBSD's bootloader only works on a New World system.
The simplest way to distinguish a New World ROM Mac is that it will have a factory built-inUSB port. No Old World ROM Mac had a USB port as factory equipment; instead, they usedADB for keyboard and mouse, and mini-DIN-8 "modem" and "printer" serial ports for other peripherals. Also, New World ROM Macs generally do not have a built-infloppy drive.