Power MAC G5 and G4. How can I delete all files from these without using the trash option?

Thank you for the information.

Since the Mac Pro (2008) is not a Power Mac, you may want to have a look at applicable sections of the following articles:

What to do before you sell, give away, or trade in your Mac - Apple Support

Use Disk Utility to erase an Intel-based Mac – Apple Support (UK)

https://www.macworld.co.uk/how-to/mac-recovery-mode-3674052/

For the older G3 or G4 Mac, you would need a bootable system/utility disc. If not available, there once was a downloadable ISO-file (dban-2.0.0_powerpc.iso) that could be used to burn a bootable CD containing a third-party free wiping utility for PowerPC models. Otherwise, you could also remove the hard drive from the computer (this may be more or less complicated, depending on the exact G3 or G4 model). If the G3 or G4 model is working, and has a FireWire port, there may be other possibilities as well.

You're welcome!

I should add that Macs with FireWire ports can use (FireWire) target disk mode.

Transfer files between two Mac computers using target disk mode – Apple Support (UK)

This means that one computer could act as an external hard drive when connected to the host. That can be useful if one wants to gain access to the target computer hard disk by running a utility from the host.

A Mac Pro 2008 has FireWire ports, a G3/G4 may have, and (depending on the model/year) a Mac mini may as well.

Hi,

Any information about the exact models/years?

https://everymac.com/systems/apple/index-apple-specs-applespec.html

Do you have access to system discs for these computers? If so, versions?

Do you just want to (securely and completely) erase/wipe the hard disks, or do you also wish to reinstall the operating systems?