I can't for the life of me figure out how to boot from a CF card either in a PCMCIA adaptor or using a USB adaptor. I can hold down option and see the main volume but the CF card formatted HFS+ cant be seen. Its blessed but just wont boot. Any ideas?
Which Mac, specifically? Many, but not all, NewWorld Macs can boot from USB. The BlueWhite G3 and the colored iBooks, tray-loading iMacs, and at least the PCI Graphics ("Yikes!") PowerMac G4 are unable to boot from USB. At all.
Here's my experience booting from usb on a NewWorld Mac. On my pismo about 6 years ago, my dvd drive went out. Then I somehow broke my OSX install, I don't remember how. I was not able to use an external USB cd rom to boot into OSX. (Probably Panther or Tiger). I was however able to boot into OS9 and install it. That's my two cents on the issue.