format ibook g4 with broken cd drive, without firewire?

The two main pathways to access an internal hard disk drive in a powerPC Mac portable such as the iBookG4 and others, would be the optical drive for use of disk utilities on disc media, or system boot install-restore discs; then the FireWire400 port is another method of fast data transfer and access via Target Disk Mode that offers a few options to attempt to perform disk drive maintenance, and perhaps install another system through use of another computer that can either be used as an optical drive for the one with failed combo or superdrive. Or there is a way to try & use the Target Disk Mode with the iBook booted into TDM so its HDD is like an external drive to another computer, and this other one may act as a host and facilitate the installation.

{Or if you had a suitable self-powered oxford-chipset equipped FireWire400 enclosure with a good hard disk drive, and set about using a utility such as Carbon Copy Cloner from Bombich online, where the software works free to make basic clones (of the system in the iBook) and this external drive would best be set up with a few partitions, so you could so more than just have a bootable clone of the iBook's current stuff in there; it could do quite a bit.}

Sounds like the poor iBook needs some technical assistance, or some extensive

DIY with some repair guides and correct replacement parts in hand. Have you

looked into some guides at ifixit.com to see about trying it?

The USB port speed may be marginal for use of an external USB optical drive, and older powerPC were marginal or not supported with USB boot devices; but there are some out there which may support use of the OS X install-restore discs that are DVD. Some are relatively inexpensive, such as one by LG, and the Apple USB external superdrive may be too new, as it is more attuned to later intel-Macs that don't have a built-in optical drive. However, several powerPC models do not boot from USB. They prefer FW400.

So short of trial and error, I'm not certain there is another way around the need for using the FW400 port, or the built-in optical drive; if you don't have a suitably able second Mac to try the FW TDM, and known-good firewire cable. The hardest way would be to take apart the iBook and put its hard disk drive into an enclosure that could use the ATA/IDE drives (not newer ones that see SATA) so as to access the HDD from another Mac and do the formatting, try to install an OS X, and other software, then reinstall the HDD to the iBook.

Most of the questionable steps could be tested, such as the iBook HDD in an external enclosure, as a good one could use that HDD as a boot volume for the iBook, too; a clone could reside in a FW HDD enclosure. Those usually should have oxford chipsets and their own power supply. In fact if you have a FW optical drive and it won't work, it may not be of a correct chipset or other circuitry to be a boot-capable device for Mac.

Anyway, someone will likely see this and hopefully they have a better answer, without significant investment; because there are good used repaired older portable Macs with some limited guaranty for around $300. or less.

Good luck & happy computing! 🙂