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Unbelievable, but true: A slow 24X Apple CD-ROM drive costs about 300 Dollars. PC dealers charge much less for a very fast 40X drive but the MacOS refuses to work with it without a capable driver.
A little patch with ResEdit and the Apple CD-ROM software gracefully accepts any SCSI drive that's connected to your Macintosh, even the ones it normally rejects. If you have an Macintosh equipped with an ATAPI interface, e. g. a Power Macintosh G3, the MacOS already has all the software you need to operate an ATAPI CD- or DVD-ROM drive, even without a patch.
Starting with version 5.2 the Apple CD-ROM Software supports any ATAPI reader as well as the SCSI drives Apple has built into the various Macintosh systems. The latest version 5.4.2 comes as part of MacOS 8.1. Its companion extension "Apple DVD-ROM 1.0" exclusively handles ATAPI DVD-ROM drives. MacOS 8.5 combines these two extension into the "Apple CD/DVD Driver 1.01". It can drive any ATAPI CD- and DVD-ROM drive as well as all the SCSI drives Apple has ever used in their systems.
The CD-ROM driver 5.4.2 can be extracted from the file "Tome1" of the MacOS 8.1 Update using Apple's TomeViewer. The latest version of the "Apple CD/DVD Driver" is 1.2 which comes as part of the Apple DVD Software Update 1.1. Using TomeViewer you can extract it from the file "Apple DVD Software Tome".
When it comes to SCSI drives, the picture changes. Drives not recognized by the software are simply ignored by the driver - with one notable exception: Apple CD-ROM 5.3.1, which ships as part of MacOS 7.6, offers generic support for 6x or faster SCSI CD-ROM drives. This enables non-Apple CD-ROMs with a SCSI interface to mount CDs without the presence of an additional third-party driver such as the FWB CD-ROM Toolkit or the Intech SpeedTools. Unfortunately, this driver is not perfect. With some drives, e. g. the Pioneer DR-U06, it fails to skip titles while playing music from Audio-CDs. Sequentially playing music titles works fine though, as well as digital audio extraction.
Applying the patch with ResEdit should be easy. Afterwards the Apple CD-ROM 5.4.2, as well as Apple CD/DVD Driver 1.01 and 1.2, can be used with any SCSI drive. The respective system extension contains two resources of type "DRVR", one with ID = 32 which handles SCSI drives while the other with ID = 33 handles their ATAPI cousins.
Which drives are supported is hard-wired inside the driver. Nevertheless, only three bytes have to be changed to transform the stubborn driver software into an "I-accept-any-SCSI-drive" version. Using ResEdits "Open Using Hex Editor" command, open the DRVR-resourve ID=32 and change three bytes according to the following table. Please make sure that the length of the resource does not change. As with anything you do in ResEdit, it is mandatory to work only with copies, never the original file.
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| Change from $67 to $66 at offset |
$06B6 |
$0A1A
$06C8 |
$06C6 |
| Change from $66 to $67 at offset |
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The Apple DVD-ROM driver 1.0 from MacOS 8.1 accepts only ATAPI DVD drives, so an adaption to SCSI devices is simply impossible. The CD/DVD drivers 1.01 and 1.2, on the other hand, will accept SCSI CD drives as well as SCSI DVD drives after applying the patch. You can even read CD-ROMs with the patched driver using DVD-RAM drives and CD-Writers. For writing to these media you will still need specialized software like the DVD-RAM-Tuneup from Software Architects or Adaptec's Toast.
The modified software has its caveats. Like the Apple CD-ROM driver 5.3.1 it has problems skipping tracks on Audio CDs on certain drives and it ignores the Apple drives it once accepted. If you want to use an Apple-supplied CD-ROM drive as well as other models simultaneously, you simply have to put an original and the modified driver into the Extensions folder. The unpatched version takes care of the Apple drive whereas the universal driver handles all the drives the Apple software rejects. (adb)
