MFS support

[boredzo]

Inside Macintosh Volume II defines what we now call the Macintosh File System, the predecessor to HFS.

It might be cool to at least be able to extract files from MFS volumes.

I have no idea how one would go about verifying the extractions. Could try DeRezzing any files with resource forks, I guess.

[boredzo]

An alternate method (or perhaps one way to verify extractions) would be the MFSLives Apple sample code, which exists in slightly updated form at https://github.com/leiless/MFSLives . MFSLives builds an FS plug-in that can be installed to /S/L/Filesystems, where the plug-ins for HFS(+) et al normally reside.

[boredzo]

This would help answer a few questions I've long wondered about, which I've never had satisfactorily answered because I've never used an MFS system myself and all the writing about it has been game-of-telephone of multiple statements of varying technical accuracy.

• Is it possible to create a folder on an MFS disk? That is, if I insert an MFS disk, does the Finder have a New Folder command that exists and works?
• Are folders persistent or ephemeral? I've often heard them characterized as ephemeral (they'll disappear when the disk is unmounted), but I'm not sure about that. This article says they're actually persisted in the Desktop file.
• Was it always possible to create folders on MFS? Could this have been a feature that was added along with HFS, and the Desktop-file implementation of folders was a way to make folders possible on MFS disks where they previously weren't? Or did folders always exist, and the people who asserted folders didn't exist until HFS simply got it wrong?
• What, exactly, are the requirements for HFS to be available? Possible requirements include particular Mac models, particular ROM versions, particular ROM sizes (64K vs. 128K), and OS versions.

I haven't tested the MFSLives plug-in nor otherwise investigated whether it might support retrieving folder info from the Desktop file. (Doing that would, of course, require support for parsing the Desktop file… which, if MFSLives implements it, it would have to have code for…)

[boredzo]

“Hard Disk Management for the Macintosh” (https://vintageapple.org/macbooks/) mentions that MFS didn't let you nest folders. So there's another thing to test.

It also says:

The HFS was introduced in January 1986 before the Mac Plus with Apple's HD 20 (as System 3.1 and Finder 5.1). At that time it was in software. With the Mac Plus or ROM upgrade, code for the HFS has been put into ROM and works much more quickly. The HFS works well without the new ROM (on a fat Mac with a hard disk, for example), but it will be slow.

So that answers that. (The “ROM upgrade” it refers to is the difference between a Mac 512K and a 512K Enhanced. You could swap out the 64K ROM for a 128K ROM equivalent to the one from a Mac Plus. Among other things, it added support for the 800K drive.)

[boredzo]

Experimenting in a Mini vMac configured to be a 128K, I've confirmed at least that folders do persist, whatever the mechanism was. And also you can totally put folders into other folders, so I don't know what that assertion was about. This is on System 1.1.

[boredzo]

The Hard Disk 20 manual includes this tidbit on page 30:

With 3½-inch disks, if the Finder has an error and can’t reconstruct your folders exactly as they were, the top level of the folder hierarchy will be remembered (although the names will be lost and the folders will be renamed # 1, # 2, and so forth).