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Build the PowerPC part of the NewWorld Mac ROM

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Elliot Nunn 4c0e5221f1 Remove unnecessary static branch hints These + and - characters in a branch mnemonic can cause the assembler to produce conditional branch instructions with that hint the branch predictor. The default for forward branches is -, and for backward branches is +. If a mnemonic is issued with the opposite sign, then bit 10 of the instruction (the LSB of the BO field) is set. My long-retired "ppcdisasm" script inserted these hints unconditionally, despite 98% of them not being required. The code is much cleaner now. I read in some old MPW release notes that PPCAsm and PPCLink together exhibit a quirk when linking conditional branches to imported symbols. PPCAsm always assembles these conditional branches as if they were forward branches (that is, a + hint will always set the hint bit, and a - hint will never). I hoped to use this property to divine whether the NanoKernel was linked from one or many assembly files, but I was frustrated by the lack of conditional branches between files.		2018-04-15 16:52:14 +08:00
BuildResults	Initial commit	2018-02-18 01:24:10 +08:00
Internal	Work on the scheduler and interrupt handling code	2018-03-30 10:27:12 +08:00
Linker	Initial commit	2018-02-18 01:24:10 +08:00
NanoKernel	Remove unnecessary static branch hints	2018-04-15 16:52:14 +08:00
.gitignore	Initial commit	2018-02-18 01:24:10 +08:00
ConfigInfo.s	Initial commit	2018-02-18 01:24:10 +08:00
EasyBuild	Initial commit	2018-02-18 01:24:10 +08:00
Emulator.x	Initial commit	2018-02-18 01:24:10 +08:00
MakeFile	Initial commit	2018-02-18 01:24:10 +08:00
PPCExceptionTable.s	Initial commit	2018-02-18 01:24:10 +08:00
README.md	Initial commit	2018-02-18 01:24:10 +08:00
RomMondo.bin	Initial commit	2018-02-18 01:24:10 +08:00
SetFileTypes.sh	Initial commit	2018-02-18 01:24:10 +08:00

README.md

The PowerPC ROM for NewWorld Macs

This repo is part of the CDG5 project. It builds a 4 MB PowerPC Mac ROM by appending PowerPC code to a 68k Mac ROM (either the included dump, or one that you built yourself). The build result is a byte-perfect copy of the ROM inside the final "Mac OS ROM" release.

Fixing line endings

MPW requires old-style Mac line endings (CR), while Git works better with Unix line endings (LF). Git filters can be used to convert between the two. Files committed to the repo are "cleaned" (LF-ed), and then "smudged" (CR-ed) when they hit the working tree. After cloning, append these snippets to your Git config.

Append this to .git/config:

[filter "maclines"]
	clean = LC_CTYPE=C tr \\\\r \\\\n
	smudge = LC_CTYPE=C tr \\\\n \\\\r

Append this to .git/info/attributes:

* filter=maclines
*.* -filter
*.s filter=maclines
*.a filter=maclines
*.c filter=maclines
*.h filter=maclines

Finally, do a once-off "re-smudge":

rm -rf ../powermac-rom/*
git checkout .

Setting type and creator codes

Some MPW Tools require their input files to have the correct Mac OS file type, but Git does not save Mac OS type and creator codes. This shell script will give enough files a "TEXT" type to keep MPW happy.

sh SetFileTypes.sh

Building

This code is built with the Macintosh Programmer's Workshop (MPW), which runs on the Classic Mac OS. To satisfy the memory requirements of the build process, the MPW Shell should get a memory partition of at least 16 MB. Once you have MPW set up, the build process is not particularly fussy.

Not many computers run the Classic Mac OS any more. Here are a few workarounds:

Just find a Mac running Mac OS 7.5-9.2. (Not much fun if it's also your test machine.)
Use the Classic environment on a PowerPC Mac running Mac OS X 10.4 or earlier. (A small PowerBook or iBook is perfect.)
Use EMPW ("Emulated MPW"), a package of command-line tools, emulators and OS images that lets you run MPW commands straight from your macOS Terminal. This is my preferred solution.

Once MPW is set up, the build command is:

EasyBuild

Using EMPW, that's:

empw -b EasyBuild

The 4 MB image will be at BuildResults/PowerROM.

What's next?

On NewWorld Macs, this image is extracted into RAM from a "Mac OS ROM" file at boot. Use https://github.com/elliotnunn/newworld-rom to build such a file.