Power Mac G4 with Prohibitory Sign on Startup

Hi all,

A while ago, I started getting kernel panics with my QuickSilver Power Mac G4. Now, I get the prohibitory icon on startup. I tried booting off an iBook G4's hard drive with the iBook in target mode with the same result. I then tried booting the iBook off the Power Mac's hard drive with the Power Mac in target mode and met with success. I am currently backing up the Power Mac's files to the iBook using the ditto command.

Where should I start trouble shooting? The only external peripherals I have besides my Acer monitor are a Goldtouch KeyOvation keyboard, a Microsoft mouse, but unplugging them has no effect.

I can try removing one of the two memory sticks or disconnecting the optical drive once the backup is complete and booting up the Power Mac on its own.

Thanks!

I know the G5 iMac's were plagued with bad capasitors ... have not had too many G4 QuickSilvers pass my way but I do have one running in the basement for back ups .. but is it possible there is an issue with the logicboard that is similar? you are on the right track starting with any external stuff.. and memory ... one stick at a time .. after backing up all the files you may want to start clean and fresh with the install disks and see if that helps with a fresh install. Hope its not something catastrophic.

Thanks for your reply, Ce. I'll try the memory and the optical drive when I get home.

You need to boot the machine with the install disc and repair the hard drive and permissions. If all that checks out ok ..move on to the memory sticks.

SK, is successfully putting the machine into FireWire target mode and booting a different Mac from the machine, then unsuccessfully doing the reverse not enough to rule out hard drive issues?

No. Mac_SK gave you the best advice but of course you do own your own onstall discs?

After the first kernel panic you should have repaired the machine..you should have OnyX installed.

Hi all,

Thanks for your replies. I've got the install discs somewhere. We've been in the process of moving, and the install discs are in a box somewhere, so I cannot use them for now.

Does Disk Utility do less than what comes on the install disk? I booted the iBook from its own drive, connected to the Power Mac in target disk mode, and ran Disk Utility to no avail. I did try isolating the problem to a piece of user-serviceable hardware (RAM, DVD, etc.) to no avail.

As for what I should have done, yes, of course I should have repaired it, but I didn't, so here I am.

SK, can you explain why the test I did with successfully booting the iBook from the Power Mac's hard drive and then switching the two for a failure is insufficient? I'm not being facetious. I'd like to know what I missed. Is the iBook's system software not capable of booting the Power Mac?

Is always better to repair a HD from locked media. Its difficult for Disk Utility to repair like B-tree issues if its running on the HD your trying to repair. Your two different Macs run off different firmware also different apps. Something like a corrupt printer driver could stop the boot. When the machine starts up it test the system hardware and OS..if theres a problem ..kernel panic. The boards are designed differently from each other. ..a different laptop model may boot or may not..everything in the OS has to be just right. Theres an issue with the G4. A kernel panic after start up suggest that important system files are corrupt or missing on the root level of the HD..mach_kernel. So you may have corruption issues with both the G4 and iBook.