Reading Old Mac Floppy Disks

02/23/2018 22:58:10


My family’s first computer was the original 128k Mac. Black and White. 512 x 342 pixels. And a floppy drive that managed to squeeze 400k onto a disk that normally holds 360k.

Which was great back then because swapping floppy disks back and forth was terrible. Anything that allowed one to put an extra document on the disk was great!

… until you need to try and access read those disks years later.

Brief Tech Note

There are other sites that do a great job describing the technical aspects of the early Mac floppy drives (here and here). So I won’t go into the details, but the short version is:

  • 400k floppy disks were formatted using the Macintosh File System (MFS)

  • These disks require an Apple drive

  • 800k disks were formatted using Hierarchical File System (HFS)

  • 1.4 MB disks were formatted with HFS+, and can be read on “any” 3.5 inch floppy drive, not just Apple drives.

  • MFS disks could no longer be read after OS 7

  • HFS disks can still be read, but cannot be written after 10.5.8

The Problem

I still have a few of my old floppy disks sitting around. Many of them have disappeared over the years, but a few survived. A while back I tried to copy as many of my important documents to my hard drives. But a few disks didn’t make it.

Then Mac computers stopped coming with internal floppy drives, and then I realized that I no longer had any working computers with floppy drives. So there was no longer any way to read those disks.

No big deal, the data wasn’t that important…. Until I discovered the rabbit hole that is emulation (e.g. Mini vMac, QEMU, and of course, VirtualBox). I realized that I could restore my old Mac Plus from the dead as a virtual machine, and run the old software from my childhood.

Except I didn’t have those disks in a readable format… I bought a USB floppy drive that reads PC disks and 1.4 MB disks fine, but would not read my old 400k/800k for the reasons described elsewhere.


Researching online suggested that:

  • There are still powerbooks to be had on eBay that have internal floppy drives.

  • Some of these machines even work

  • Working machines with MacOS 7 would allow me to read MFS disks, but newer systems would not

This limited the number of options. But I did read that a newer machine, despite not being able to read 400k MFS disks was able to write a disk image to one, and that disk could then be read on an older machine.

So I figured all I really needed was a machine with an internal floppy drive, and some software that would allow me to image a disk, even if that computer couldn’t understand it.

My Approach

After some trial and error (eBay can be frustrating) I ended up with a working G3 “Wallstreet” Powerbook. I would have been using a 520 model and a Mac clone at this time, so it wasn’t a computer I owned before.

After getting the machine to boot (more frustration), I found that the floppy drive did in fact work, and I was off.

  1. I used Apple’s Disk Copy program to image my floppy disks

  2. I saved the images in the Disk Copy 4.2 format

  3. I then put the images on a 1.4 MB floppy that could then be read on both the G3 and my modern desktop with a USB floppy drive

  4. (I could theoretically get the G3 up on my LAN and find a way to share files, but that seemed like to much trouble at the moment.)

  5. I copied the DC 4.2 image to my Mac OS X desktop.

  6. I then used Mini vMac (running either OS 7.5.5 or 6.0.8) to read the disk images. I could access the files and folders on most of my disks.

  7. A few disks failed to copy. After much digging around, I found reference to a program called DiskDup from “back in the day”. After telling it to allow a few sector errors, it was able to read the remaining disks (except for two) and convert them to DC 4.2 format

Copy Protection

Some of these games had copy protection. Zork I, for example, limits your ability to copy the application from the disk, but imaging the entire disk worked. Zork II and Zork III, however, request that you insert the master copy (which I can’t do on a Mac OS X machine, of course.)

Most classic abandonware games can be downloaded somewhere. There are great repositories out there:

In the case of my games, the short version is that I wanted to try and be able to use the save games I had on the floppies (for no real reason, I just like a challenge sometime.) I was able to get Zork I to work, a version of Moonmist I found elsewhere was compatible with my save games, but the versions of Zork II/III I found are not compatible with my save game files. I’m still working on that…

Obsolete File Formats

The other problem one might run into is file formats that are no longer supported (e.g. MacWrite 2.20 for example.)

Many old programs can be found online, or you might be able to restore them from an old floppy. But if you can get an old version of the software running in an emulator, you may be able to “leapfrog” the document from an obsolete format to a more modern one (something like MacWrite 2 -> MacWrite 5 -> Word). Or perhaps a good translational format (such as RTF – I know, I rant about how terrible RTF is, but this is the one valid use.) You might not get the exact formatting, but can get it pretty close.

Failures/Next Steps

As above, so far there are three disks (two senate games) I was unable to access:

  • Hitchhiker’s Guide to the Galaxy – the app can be found elsewhere (including the Solid Gold version, no less!), but I wanted to run my copy. DiskDup is struggling to be able to image that disk, but I haven’t given up hope.

  • Fahrenheit 451 – I found that game online but it wouldn’t run. Disk Copy worked on the first disk, but not the second. But the image couldn’t be read, so in fact neither disk has worked so far.

My next step is to try running Copy II Mac, which seems to support more options for corrupted disk sectors which were sometimes used as copy protection, but it seems that program won’t run on my OS 8.5.1 laptop. I’m looking for a way to try it on an OS 7 machine since that might solve a few issues.

Take-home Points

The main contribution here is that you can actually gain access to 400k MFS- formatted floppy disks with a newer computer that can’t actually read those disks using the imaging technique above. This opens up the range of vintage macs that can be used for data recovery to include some newer (and probably more readily available) machines.

Plus, it was fun to see some of the old software I had played with as a kid, whether it be commercial stuff I spent way too many hours on, or early gems from when I discovered shareware.

Update 2018–02–24

It occurred to me to try rebooting with extensions off, and that did allow Copy II Mac to run. However, it is only able to copy one floppy to another – it doesn’t make disk images.

Which lead me to exploring the “cracking” tools from 30 years ago. Ended up finding a “How to Crack” guide by “The Shepherd”, which as a walkthrough demontrated how to use MacNosy to break the encryption on Sorcerer. It appears that the master disk encryption for that game is the same as Zork II and Zork III (they are probably the same wrapper app with different data files). However, after making the required change, the app simply crashes a little bit later.

I also stumbled across the Floppy Emu, which appears to replace a floppy drive in old Macs with a SD card drive.

Theoretically, if this were installed as the external drive, then Copy II Mac would be able to copy a Copy Protected (or slightly corrupted) disk to the Floppy Emu, where it would be stored as a disk image. This disk image, could possibly then be loaded onto a virtual Mac as a floppy that may or may not work. While interesting, I don’t have an old enough Mac for it to work, nor is it additional money on something I don’t need to do…. But it would be interesting to know if it works!

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