Third-Party Optical Drive Support

What is this mod for?

System 7, OS 8, and OS 9 use custom CD/DVD drivers that will normally only work with specific optical drives. While there has been third-party software in the past to support other drives, there are a lot of models found on eBay and elsewhere that still aren't supported.

Fortunately, there's a very simple edit that can be made to the operating system's native CD/DVD driver to support just about any optical drive you can find.

Required tools

This modification requires ResEdit or another resource editor (although ResEdit is free, so that's probably your best option).

You also need to identify what version of the Apple CD/DVD driver you have installed. The easiest way to find this in OS 8 or OS 9 is to use System Profiler. In System 7, it's a little bit harder. You can try something like TattleTale or Tech Tool Pro to get the version of your driver.

The following driver versions support this mod:

  • CD-ROM 5.4.2
  • CD/DVD Driver 1.0.1
  • CD/DVD Driver 1.2
  • CD/DVD Driver 1.2.2
  • CD/DVD Driver 1.3.1
  • CD/DVD Driver 1.3.5
  • CD/DVD Driver 1.4
  • CD/DVD Driver 1.4.3

Please note: driver versions 1.3.1 and higher use the same values for the mod.

Mod instructions

First, make a backup of the system extension!! You'll be working on a copy of Apple CD-ROM or Apple CD/DVD Driver found in your Extensions folder.

Open a copy of the driver in ResEdit. Look for the resource icon titled DRVR and double-click it to open.

In the window that appears, select ID 32 and select Open using Hex Editor from the Resource menu item.

In this window, use Find > Offset, or Cmd+H to navigate to the appropriate offset listed in the table below. You will need to change the value of the offset as shown:

Driver Version Row Offset Original Value New Value
5.4.2 06B0 06B6 6704 4E71
1.01 06C8 06C8 6704 4E71
1.2 06C0 06C6 6706 4E71
1.2.2 06D8 06D8 6706 4E71
1.3.1+ 06D0 06D6 6706 4E71

Once you've made the above change, save the file and then proceed to the next offset and make the listed change:

Driver Version Row Offset Original Value New Value
5.4.2 09C0 09C6 6606 4A84 6700 0086 4E71 4E71 4E71 4E71
1.01 0A10 0A10 6606 4A84 6700 0086 4E71 4E71 4E71 4E71
1.2 0AD0 0AD6 6604 4A84 6706 4E71 4E71 4E71
1.2.2 0AE8 0AE8 6604 4A84 6706 4E71 4E71 4E71
1.3.1+ 0AE0 0AE6 6604 4A84 6706 4E71 4E71 4E71

Save again. Make sure that the modified extension is in your Extensions folder - not the original - and reboot. Your “unsupported” drive should work now!

wiki/hardware/3odd.txt · Last modified: 2023/10/10 17:51
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