iMac G3 2001 issue with "modern" slim DVD-RW

[indibil]

Hello! I need your help.

I have an iMac G3 500@650MHz with OS 9.2.2. The original optical drive struggles to read discs, so I've adapted an original ATA slot-in laptop DVD-RW unit from a Mac Mini G4. I had the DVD holder from an iMac G5 and with it added on top of the original iMac holder, I managed to fit it into the slot in the case, and with a 50-40 pin ATA adapter I connected it along with an SSD. The drive works perfectly, it reads both CDs and DVDs, I just need to try recording, but that's not the problem.

The problem is that the Firmware of the equipment does not recognize this optical drive as bootable, no installation disk boots either by pressing C or by pressing the ALT key. This already happened to me years ago, with my first G4, it was a Gigabit Ethernet with a DVD drive, which I replaced with an HP CD-RW, which worked great, but did not allow booting from any disk.

Is there a way to "modify" the iMac Firmware so that it recognizes the drive as bootable? This reader allows to boot without problems in the Mini G4.

Thank you!!