The Mac ROM-inator kit adds 1 MB of rewritable flash memory to your vintage compact Macintosh. A bootable ROM disk is one of many interesting possibilities this creates. The kit comes with a preprogrammed System 6.0.8 boot disk image, but how can you edit the disk image or replace it with a different one? My previous description skipped over some steps that may not have been clear to everyone, so read on for a detailed tutorial on creating and transferring the disk image.

 
Creating the Disk Image

The first step is to download or create a new disk image file, to be used for the ROM disk. These files normally end with a .dsk filename extension, and are commonly used with Macintosh emulation tools and disk copy programs. The Floppy Emu disk emulator also uses .dsk files, so if you’ve already got an Emu, you can probably use one of your existing disk image files as a ROM disk. You can also download .dsk files for many old system versions, utilities, and games at tkc8800.com. As long as the file isn’t larger than 864K, and contains bootable system software, it should work.

But using an existing disk image is boring. What if you want to create a custom disk image, with your own personal collection of games? There are many ways to do it, including the tools HFVExplorer (Windows) or Fuse HFS (OS X). The method I’ll describe here uses a popular software-based Macintosh emulator called Mini vMac. We’ll use this software to set up a new .dsk file, and fill it with goodies.

1. Download Mini vMac here. It supports OS X, Windows, Linux.
2. Before you can run Mini vMac, you’ll need a Macintosh ROM file (vMac.ROM) and system disk. You can find both in this tutorial file archive.
3. Move vMac.ROM into the same folder as the Mini vMac application you just downloaded, and follow the setup instructions. When the instructions ask you to drag your bootable disk image, use the file HD20.dsk from the previous step’s file archive.

You’re now running an emulated Mac Plus! You can attach additional disks by simply dragging the .dsk files into the Mini vMac window. Unlike a real Plus, you can have many disks attached all at the same time. Let’s create a bootable disk image for use with the ROM-inator, containing a few classic Mac games.

4. The archive contains an empty 864K disk image file called rominator-disk.dsk. Drag this file into the Mini vMac window.
5. Download .dsk files for Klondike, Brickles, MacMan. Drag these into the Mini vMac window too.

You should now have five different disks mounted in Mini vMac:

6. In Mini vMac, drag the System Folder from the System Startup Disk to ROM-inator Disk. This copies the system software, and makes ROM-inator Disk a bootable disk.
7. Copy the games from the other disks onto the ROM-inator Disk. Some of the game disks also contain System Folders. Don’t copy these – only copy the games themselves.

You should now have a finished ROM-inator Disk:

Drag the ROM-inator Disk icon to the trash can to unmount it. Your finished ROM disk image is now stored in the file rominator-disk.dsk.

 
Transferring the Disk Image

Now that you have a disk image file, how do you get it onto your Macintosh so you can write it to the ROM-inator? Once again there are several ways to do it, including connecting your compact Mac over Localtalk to a slightly less ancient Mac that also has Ethernet, or using an external SCSI drive to sneakernet the file from another computer. But the simplest method is to use a Floppy Emu configured as a hard disk emulator in HD20 mode.

Normally you would copy a .dsk file to the Floppy Emu’s SD card, so you could use it on the Macintosh as if it were a real disk. But in this case, we actually want the .dsk file itself transferred to the Mac, which means we need to put the file rominator-disk.dsk inside another disk image. We’ll use Mini vMac again.

1. Start Mini vMac.
2. When you see the blinking question mark, drag HD20.dsk into the Mini vMac window.
3. In Mini vMac, on the System Startup Disk, you’ll find a program called ImportFl. Double-click the icon to run it.

ImportFl will now wait for a file to import from the host operating system:

4. From your OS X, Windows, or Linux desktop, drag the file rominator-disk.dsk into the Mini vMac window.
5. When prompted, choose a destination on System Startup Disk to save the file. Any location is fine – just remember where you put it, so you can find it later.
6. Quit ImportFl.

rominator-disk.dsk is now stored as a data file, inside HD20.dsk.

7. Exit Mini vMac.
8. Copy HD20.dsk to Floppy Emu’s SD card.
9. If you haven’t already, update your Floppy Emu with the latest HD20-aware firmware. You can download the firmware from the Floppy Emu product page.
10. Connect the Emu to your Mac, and turn it on. If necessary, press SELECT while the Emu is displaying version info on the LCD, in order to switch into hard disk emulation mode.
11. Reset the Mac. It will boot from the HD20.dsk image on the SD card.

rominator-disk.dsk is now visible as a regular file, on the System Startup Disk mounted by your Mac.

 
Writing the Disk Image

The final step is the easiest – writing the new disk image to the ROM-inator. The utility program Flash Tool makes this easy, and to make it even easier, Flash Tool is already included in the HD20.dsk image.

1. On your Mac, on the System Startup Disk, you’ll find a program called Flash Tool. Double-click the icon to run it.
2. Under the heading “ROM Area to Update”, select ROM Disk Image.
3. Press the Select File… button, and browse to the location where you previously stored rominator-disk.dsk. Select this file.

The Flash Tool setup should now look like this:

4. Press the Update ROM button. You’ll see a progress bar while it’s working. The update takes about 60 seconds.
5. When the update is finished, reset your Mac.

You’re done! It looks like a lot of steps, but the whole process only takes a few minutes. Your new disk image is now stored in flash memory by the ROM-inator. Whenever you turn on your Mac, you’ll see the “press and hold R now” message. To boot from the ROM disk, press and hold the R key on the keyboard for a few seconds. If R is not pressed, the Macintosh will boot normally from an attached SCSI disk, or wait for a floppy disk to be inserted.

Have fun!