"Illegal instruction" at startup

Phillip, welcome to Apple Discussions.

You may find a solution here.

Troubleshooting Address and Illegal Instruction Errors During Startup
http://docs.info.apple.com/article.html?artnum=24815

A great site for info on the 6400 (&6500) is at the 6400 Zone at http://www.zone6400.com

Cheers, Tom

Try to restart with some extensions off to find wich one is the wrong.
Make groups to find the extension easely. I know is a slow work but you have to find wich one is wrong!
Every time you disble the extensions you've to restart to look if the systems runs or not.

Then when you know the wrong extension change it for another not corrputed.

Hope this helps...
Xavier

Phillip-
I haven't booted from Classic for two years but I remember having the same problem on occasion.

This procedure usually corrected the problem:
(1) check all cables, terminations, addresses for all SCSI peripherals;
(2) using Norton Utilities' Disk Editor, make the Desktop visible, trash it;
(4) from the Preferences folder, trash the Finder Preference;
(3) insert a boot disk with Disk Warrior and/or Norton Utilities on it;
(4) zapp the PRAM using TechTool Lite, which finishes with a restart;
(5) hold down C on the startup;
(6) from the boot disk, run Norton Disk Doctor and/or Disk Warrior;
(7) restart to hard drive.

If that didn't correct the problem, perform a clean install.

If the problem persists, remove and replace the Extensions at a one half replenishment rate.

If none of these procedures work, then I would believe there is a hardware problem such as bad RAM, logic board, etc.

Fred


PB G4-10.3.8/9.2.2; eMac G4-10.4.5; PowerPC 6100-9.1; PB 5300-7.6.1