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Archive for the 'ROM-inator' Category

ROM-inator Back in Stock

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The Mac ROM-inator kit is back in stock! The ROM-inator replaces the stock ROM with 1MB of re-writable flash ROM in a Macintosh Plus, 512Ke, 512K, or 128K – making it possible to do all sorts of crazy customizations! The new kit has an updated default ROM image, with a new boot chime, modified Happy Mac icon, and System 6 ROM disk with a small collection of built-in apps and games. All these defaults can be changed by updating the flash memory. Personalize that old compact Mac, and make it fun again!

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ROM-inator Disk Setup Tutorial


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 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.

  1. The archive contains an empty 864K disk image file called rominator-disk.dsk. Drag this file into the Mini vMac window.
  2. 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:


  1. 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.
  2. 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:


  1. From your OS X, Windows, or Linux desktop, drag the file rominator-disk.dsk into the Mini vMac window.
  2. 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.
  3. Quit ImportFl.

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


  1. Exit Mini vMac.
  2. Copy HD20.dsk to Floppy Emu’s SD card.
  3. 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.
  4. 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.
  5. 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:


  1. Press the Update ROM button. You’ll see a progress bar while it’s working. The update takes about 60 seconds.
  2. 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!


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Hacking the Happy Mac

Anyone who used a Macintosh in the 80’s or 90’s remembers the Happy Mac icon – the smiling computer face that appeared on the screen while the machine was booting up. With my new ROM-inator flash memory kit for vintage compact Macs, hacking the Happy Mac icon is easy. The happy face is stored as a 20 byte raw bitmap, beginning at offset $FD2 (hex) in the ROM code file. It’s a 16 x 10 rectangle within the “screen” area of the surrounding Macintosh icon.

All of the icons above can be downloaded from the ROM-inator page. I went with the sunglasses for my Mac Plus, ’cause that’s how I roll…

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Introducing the Mac ROM-inator

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Today I’m excited to introduce a new product: the Mac ROM-inator kit. The ROM-inator replaces the stock 64K or 128K of ROM in a compact Macintosh with a full 1 MB of flash memory, unlocking wild new possibilities. Add and edit a bootable ROM disk! Replace the startup sound, or tweak the ROM code behavior. What’s best is the flash ROM’s contents can be updated from within the running Macintosh, allowing for crazy customization experiments. For power users, binary editing of the ROM image opens new possibilities like changing the Happy Mac icon, altering the built-in fonts, and modifying the system startup routines.

The Mac ROM-inator supports the Macintosh Plus, Mac 512Ke, 512K, and 128K. The kit includes two preprogrammed flash memory chips, with a System 6 ROM disk and a “mooo” startup sound. It’s priced at $25, and is available immediately. Get yours now!

The ROM-inator is a descendant of Rob Braun’s original Mac Plus ROM Adapter and disk driver. More details about its inspiration and development are here.


When first powered on, the Macintosh will play a customized startup sound, and display a “pirate Macintosh” icon. 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.


The 1 MB flash ROM includes 132K for ROM code, 28K for a custom startup sound, and up to 864K for a ROM disk image. The preprogrammed flash chips contain ROM code based upon the Mac Plus ROM. If used with a Macintosh 128K or 512K, it will turn them into a 128Ke or 512Ke. This will also give those machines native HD20 support, for use with Floppy Emu in HD20 hard disk emulation mode.

The utility program Flash Tool can update the flash ROM from within the running Mac. Alternatively, the flash chips can be removed from their sockets and reprogrammed using a standard EPROM programmer.

Flash Tool

To use Flash Tool, simply select the ROM area and the data file to use for the update. The program will verify that the data file is the correct size for the area to be updated. After about sixty seconds, it’s done!

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Rewritable ROM Disk for Mac Plus


Stuffing new technology into old hardware is fun. How about a bootable, rewritable ROM disk for a Macintosh Plus, using modern flash memory? Dream no more, the reality is here. 🙂 Using a small adapter board, the original ROM chips on the Mac’s logic board are replaced with 1 MB of flash ROM. The flash ROM contains a modified copy of the original Apple ROM data plus a special disk driver, and a disk image occupies the remainder of the 1 MB of flash. When powered on, the Mac can be booted from the built-in ROM disk with a single key press. When necessary, the contents of the ROM disk image can be rewritten from within the running system, using a custom-made flash updater program. You can fill the ROM disk with system software and a couple of games, or whatever you want to show off without needing a disk. The same thing should be possible for the Mac 128K and Mac 512K too.

This project is a combination of three smaller projects, two of which were developed by other people.

1. ROM Adapter Board

Swapping the stock ROMs for larger 1 MB flash ROMs requires a physical adapter, because the flash ROMs have more pins and have some signal pins in different locations than the stock ROM chips. Rob Braun designed an adapter board that fits in the stock ROM sockets of a Mac Plus, and accepts modern (well, less ancient) 29F040B flash ROM chips. In order to take advantage of the entire 1 MB, two extra wires must be connected to address pins on the CPU. This can be done using IC test clips, or by soldering wires directly to pins on the 68000 CPU.


2. ROM Disk Driver

Apple provided the Macintosh Classic with a built-in ROM disk: hold Command-Option-X-O during startup, and the Classic will boot from the built-in disk image. Rob and Doug Brown studied how the Classic’s ROM disk driver works, and developed a stand-alone ROM disk driver for vintage Macintosh computers. Originally designed for custom ROMs in Mac II-series machines, Rob updated the ROM disk driver to work with the modified Mac Plus ROM as well. It even has a custom “pirate Mac” icon at the boot screen, to remind you that you’ve got a modified ROM installed. But the disk image is fixed in ROM – to change it, you need to open up the Mac and put the flash ROM chips in an external EPROM programmer.


3. Rewritable Flash ROM

In a discussion on the forum, I proposed connecting the CPU’s R/W pin to the flash ROMs, to make in-system reprogramming of the disk image possible. By coincidence, I had just finished my 68 Katy breadboard computer, which also used a 29F040B flash ROM and a 68000-family CPU. So I knew in-system modification of the flash ROM data was possible. Writing to a ROM is a strange concept, and with the 29F040B, it will ignore standard attempts at writing. That’s a good thing – you wouldn’t want a software bug to go modifying your ROM! But if you write a series of magic “unlock” bytes to a series of magic addresses in the ROM, it will enter a special command mode. From this mode, it’s possible to query the chip parameters, erase blocks of flash memory, and write new values to the flash.

To make this happen, I needed to write a flash updater program that could run on a vintage Mac. It’s not rocket science, but it had been 20 years since I last did any real classic Macintosh programming, so it took me a while to dig up Metrowerks Codewarrior and remember how to create a “hello world” type program. The resulting tool isn’t pretty, but it gets the job done, and now the contents of the ROM disk can be modified from within the running system, or even the ROM code itself can be modified.


Want to build one of these? You’ll need soldering equipment, and an EPROM programmer to write the initial image to the flash chips.

PCB Gerber files for the adapter board – plusrom5
Flash Tool for in-system ROM updating – Flash Tool 1.1
Modified ROM image (concatenate your ROM disk image to this to make a bootable ROM disk) – modplus.bin

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