This is getting interesting... 
Back to the original question, I've done some experimenting:
In my SE/30 with Apple-branded CD 300e I put any bootable CD (I used MacOS 8.6 install), wait for it to spin up, then insert a System 7.0.1 floppy (with no CD/SCSI extensions whatsoever) and power up the SE/30: the CD LED flashes for about a second (the driver is being loaded!) then the SE/30 boots from the floppy and... voilà! The CD-ROM mounts on the desktop perfectly. I can then eject it and use any other CD -- no problem.
Tried the same with System 6.0.8... more or less the same, but instead of mounting the disk, a dialog appears asking to unlock the disk because the Desktop file can't be rebuilt
Upon cancelling that, the disk is ejected...
Anyway, a non-bootable disk (standard data CD-ROM) doesn't do the trick. The LED flashing at startup is very brief, a single blink -- nothing gets actually loaded. And no CD inserted is mounted afterwards.
With non-Apple-branded drives (Yamaha 6416 & 8424) I wasn't that lucky The bootable CDs can't get the driver loaded -- I think it does load; but upon detecting a foreign drive, refuses to work. Those drives are suported by Toast CD Reader extension 4.0.2, but at a whooping 137K I don't think is the best thing to put on a System 7 floppy. Haven't tried to toast a bootable CD with that extension as the CD-ROM driver in that disk, I think it could work.
About booting from the CD: I don't have presently any CD-ROM with suitable system for the SE/30, but with the aforementioned 8.6 disk (obviously incompatible!) the Cmd-opt-shift-backspace combo tries to boot from it, although the happy Mac quickly turns into a sad one -- as expected xx(
Once again, the non-Apple drive can't boot at all... however, I could boot Dad's PowerMac 7500 from the original 7.5.2 System disk in a Yamaha drive!
In short: get an Apple-branded CD drive, any bootable disk and your usual system floppy, and your Classic will be able to read CDs
Back to the original question, I've done some experimenting:In my SE/30 with Apple-branded CD 300e I put any bootable CD (I used MacOS 8.6 install), wait for it to spin up, then insert a System 7.0.1 floppy (with no CD/SCSI extensions whatsoever) and power up the SE/30: the CD LED flashes for about a second (the driver is being loaded!) then the SE/30 boots from the floppy and... voilà! The CD-ROM mounts on the desktop perfectly. I can then eject it and use any other CD -- no problem.
Tried the same with System 6.0.8... more or less the same, but instead of mounting the disk, a dialog appears asking to unlock the disk because the Desktop file can't be rebuilt
Upon cancelling that, the disk is ejected...Anyway, a non-bootable disk (standard data CD-ROM) doesn't do the trick. The LED flashing at startup is very brief, a single blink -- nothing gets actually loaded. And no CD inserted is mounted afterwards.
With non-Apple-branded drives (Yamaha 6416 & 8424) I wasn't that lucky
The bootable CDs can't get the driver loaded -- I think it does load; but upon detecting a foreign drive, refuses to work. Those drives are suported by Toast CD Reader extension 4.0.2, but at a whooping 137K I don't think is the best thing to put on a System 7 floppy. Haven't tried to toast a bootable CD with that extension as the CD-ROM driver in that disk, I think it could work.About booting from the CD: I don't have presently any CD-ROM with suitable system for the SE/30, but with the aforementioned 8.6 disk (obviously incompatible!) the Cmd-opt-shift-backspace combo tries to boot from it, although the happy Mac quickly turns into a sad one -- as expected xx(
Once again, the non-Apple drive can't boot at all... however, I could boot Dad's PowerMac 7500 from the original 7.5.2 System disk in a Yamaha drive!
In short: get an Apple-branded CD drive, any bootable disk and your usual system floppy, and your Classic will be able to read CDs