(Vintage 68000) Macintosh Disk Images

It is quite impossible to buy boxed old Macintosh games or other software. You may have some luck with local shops or auctions, if you live in the United States, but Macintoshes were not that widely used in Europe (at least for gaming it is). I have managed to grab some original titles from eBay (many years ago), but it seems the only option for Macintosh retro-hobbyists is to use Macintosh software archiving sites.

You can find a collection of Macintosh games from Macintosh Garden. Downloads are often directly usable with your favourite emulator or BMOW floppy emu, but sometimes you need to create a disk image. A decent resource to extensively explain the disk image formats, and how to use them, is hard to find.

The downloads you get from Macintosh Garden, and other abandonware resources, are usually in one of these formats:

• .ZIP – A zip-compressed file you should know about :) Just uncompress it and see what’s inside.
• .DSK – A “raw” format simply containing disk data without checksums or other metadata.
• .IMG - This extension is the mother of all confusions. Most likely it is a Disk Copy 4.2 format. It might be read only on your emulator, but BMOW floppy emu can also write back to the image. Confusingly .img extension is generally used for raw disk images (whereas raw Macintosh images usually have .dsk extension). And even more confusingly .img is used for newer disk image formats on Macintosh (Disk Copy 6 and later, and “New Disk Image Format” or NDIF).
• .IMAGE – Possibly a Disk Copy 4.2 image, but could be a raw HFS file system, too. If you are interested to know, BMOW floppy emu will show the format on LCD screen when accessing the image.
• .HFV – A “virtual hard disk image”. Basically just a raw file using HFS file system, but bigger in size than floppies are. A hard disk image could also have .dsk extension.
• .SIT – An old-school compressed file you could extract e.g. with StuffIt Expander for OSX. But you may not want to do it, as the .sit file often contains the game executable and support files, and you better extract them inside an emulator (or a real Macintosh). StuffIt 1.5.1 should work with System 6 and 7. If you have problems extracting .sit, try a newer version.
• .SEA – Self-extracting archive. Double click inside an emulator or real Macintosh to extract files to the folder.
• .SMI – Self-mounting image. Double click inside an emulator or real Macintosh to “mount” a virtual drive.
• .BIN – MacBinary format that can be extracted with binUnpk or StuffIt. Sometimes old Macintosh software is distributed with formats like .sea.bin or .smi.bin. Funnily enough, you need first to extract these self-extracting archives with an unarchiever first.

As you can see, the way old Macintosh software is being archived is a big mess. But there is always a way to get the software running.

If the extension is .dsk, .img or .image, you are probably good to go and just use the file with your emulator or BMOW floppy emu. If you are interested in to know the format, or perhaps want to understand why your image is not being loaded, you can…

• …put the file to BMOW floppy emu. You will see the format when the disk is accessed. And you won’t see the image listed at all if it is not raw image or Disk Copy 4.2 format.
• …check out the file size (e.g. CMD+I). Raw images should be exactly 409 600 bytes for 400k disks and 819200 bytes for 800k disks. If it is a little bit more, then there’s a good change being Disk Copy 4.2 as it contains some metadata along with the raw file system. If the size is something totally else, it could be one of the newer (compressed) formats that are not supported by Mini vMac or BMOW floppy emu.
• …open the file in HEX editor, and check if there seems to be a header that looks like one defined in Disk Copy 4.2 format specification.

In the unfortunate case a game or utility was not preserved from an original floppy as a ready to use disk image (shame on you Macintosh retro community!), we need to take some further steps. This applies to all those .sit, .sea, .smi and .bin formats. One approach is to transform the downloaded package to a disk image (e.g. game.dsk) that floppy emu can read. Or you could even copy the files to a real Macintosh floppy. Either way, read about my way to do it .