Macs that do this are termed 'NewWorld' Macs, and are equal to the set of Macs that have a built-in USB port. Starting with the iMac, Apple's improved Open Firmware implementation loads and runs a 'Mac OS ROM' file in the System Folder. Machines with fast disks and plentiful, cheap RAM don't benefit as much from a large built-in ROM. Power Macs started shipping with a 4 MB 'RISC' ROM, which has the bottom three megabytes laid out like a familiar Toolbox ROM and the remaining one megabyte dedicated to PowerPC-specific code and structures. The 'Universal' 68k ROMs contain structures describing the hardware on several supported machines, and select one of these at runtime. Subsequent Macs have progressively larger ROMs, the size doubling with every step. The Toolbox ROM also makes it hard to produce an unauthorized Mac clone, and allows a graphical interface to be shown very early in the boot process. Buggy code in the ROM can be overridden with code on disk. While the Mac still requires a disk with a System file to boot, having much of the OS in ROM saves loading it from a slow disk drive and conserves precious RAM. The first Macintosh shipped with a 64 KB ROM containing much of the high-level Macintosh Toolbox as well as low-level hardware-specific code.

Flags are declared in `:Make:FeatureList` and enabled in `:Make:NewWorld.make`. Your file will end up in `:BuildResults:NewWorld:Mac OS ROM`.Īs we develop useful patches to the ROM code, we will conditionalize them using feature flags. Set MPW's current directory to the cdg5 repo, then: The `:Make:Build` script wraps the `:Make:NewWorld.make` makefile. (Hit Command-Return or the numpad Enter key to issue the command.) Clone this repo, set MPW's current directory to your local clone, and run the script `:Tools:FixRepo` from your Worksheet: (Once we understand MPW's PPCAsm better, our annotated NanoKernel disassembly will be merged in.)īecause we deal with generously sized binaries, you should increase MPW's memory allocation to well over 8 MB before you build. Binaries are in `:Prebuilt:LateNewWorld:`, and we prefer to keep them in Rez format so that we can apply compile-time conditionals.

This repo currently uses only unlinked binaries in lieu of reversed code, but this will improve very quickly. It was put on hold for a couple of months while we moved our build system away from a motley collection of Python scripts. Reversing the ROM is an ongoing, open-ended process (and heaps of fun!). The contents of this repository can be built using the Macintosh Programmer's Workshop (MPW) into a complete 'Mac OS ROM' file, which can then be used to boot Mac OS 9.2.2 on any compatible NewWorld Mac. CDG5 is a project aiming to reverse, patch and rebuild the Macintosh NewWorld ROM.

Mac classic environment emulator