Mac OS 9.x will run on a 6100, but is tricky to install. You need a retail install CD (ie a full generic install disk, not a model specific disk) and to boot from the CD. You can't boot from Mac OS 8.6 or earlier, and then run the installer.
Is it worth running Mac OS 9.x on a 6100? Possibly if an app requires it, but most will work with 8.6. The main advantage of 9.x is the extra compatibility with OS X (eg file sharing).
Is it worth running Mac OS 9.x on a 6100? Possibly if an app requires it, but most will work with 8.6. The main advantage of 9.x is the extra compatibility with OS X (eg file sharing).