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CD-ROM: Using a Bootable CD-ROM to setup your 68k Macintosh

A few years ago I created a bootable System 7.5.5 CD-ROM image file by editing the contents of a bootable System 7 CD-ROM I have. I discovered that I could change the contents system folder to 7.5.5 and the disk would still boot. This entry describes how you can use my CD-ROM image file and edit it’s contents.

What you need

Quick Start

Download my CD-ROM image

I created my System 7.5.5 CD-ROM image by editing an image file I made from a bootable System 7.0 CD-ROM. I discovered that I could mount the CD-ROM image file in Basilisk II the same way I can a hard drive image, I then replaced the contents of the System folder with the minimal version of System 7.5.5 I originally created for my bootable drive and partition/volume images and then used the System Picker to ensure that new System software was “blessed” as the start-up system.

I have found guides online for how to create a bootable CD-ROM using Toast, but I did not have any success with those options and stopped experimenting with them once I managed to get a bootable disk using the edited System 7.0 CD-ROM image.

I may make bootable CD-ROMs for later system releases if I ever need one, but at the moment my collection is limited to 68k Macintosh Systems.

Edit the contents of the CD-ROM image

You can edit the contents of my CD-ROM image using Basilisk II, or any other program that can be used to edit HFS formatted CD-ROM images.

Write (burn) the CD-ROM image to a recordable CD (CD-R)

My CD-ROM image is NOT an ISO 9660 formatted CD, it is an HFS formatted CD, therefore not all CD recording (burning) software can be used to write my CD-ROM image to a CD-R. Personally I have been using TransMac, I tried Nero, and I tried ImgBurn and both did not work on my Windows 10 system. I was surprised by this, I had assumed that a bit was a bit when writing a CD-ROM image to a CD-R. I’m experimenting with this to see why ImgBurn likes some CDs but not others. It seems to be an issue of is the CD bootable or not.

NOTE: now that CD-Rs are themselves obsolete technology, some clarification on phrases “CD burning”, and “burn a CD”. When you write to recordable CDs a laser is used, the laser doesn’t literally “burn” your CD, the lasers instead interact with photosensitive dye. When the disc is blank, the dye is translucent, but when the dye is heated by the laser in the CD recorder (burner) that portion of the CD turns opaque. The now opaque spots on the recordable CD (CD-R) are the data “bits” that can be read.

Boot your Macintosh System

The majority of 68k System and all PPC Systems can boot from CD. Apple’s Knowledge Base’s article TA29225 states the the following systems CAN NOT boot from CD-ROM:

  • Macintosh 128K, 512K, 512Ke
  • Macintosh Plus, SE, and SE/30
  • Macintosh Portable
  • Macintosh II, IIx, and IIcx
  • Macintosh Classic

To force your System to boot from your CD drive instead of a SCSI drive or internal IDE drive you try the following keyboard combinations:

  • Hold down the “C” key, this only works for Apple brand CD-ROM drives (KB TA39718)
  • Command-Option-Shift-Delete: Bypass the device that is selected in the Startup Disk control panel; boot from the first bootable device other than that.
  • Command-Option-Shift-Delete-#: Boot from a specific SCSI ID, where # is 0 through 6
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