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iMac G3 333MHz Tray-Loading: Boot issue?

Hi,

Apologies if this isn't the right place to post this, I wasn't able to find a device subheading for this computer.

Anyway, I recently got an old iMac G3 from around 1998, its one of the early tray-loading Grape models. Every time I try to boot it up, I get a bomb error message:

I've tried restarting and booting into 'Extensions off' mode but I'm very limited in what I can do. I have disabled any and all extensions, tried rebooting with all different combinations of extensions, you name it and I've tried it!

In a last-ditch effort to fix this thing I managed to get everything on the hard drive onto a USB stick, and after getting this error from disk utility:

I booted the imac into a disc copy of Tech Tools Pro 3 to completely wipe the hard disk and reformat it in HFS+ to fix the disk issues.

And then, I used a mac os 8.9 install disk to load a fresh new install on the empty HD.

Tried booting up again... and still getting the "illegal instruction" error! (But booting with shift held down still works fine)

I think the PRAM battery is still in tact as I set the year to 2001 just in case it was another case of the 'Y2K20 bug', and its been sticking to the time and date upon multiple reboots as far as I can tell.

Not entirely sure where to go from here. I've ordered a replacement hard drive that I'm going to use in the mac, so if its a bad drive hopefully that should fix it - is there anything else I can try in the meantime?

Thanks!

iMac Pro

Posted on Aug 28, 2020 4:27 PM

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Noje999 Author

Level 1

4 points

Posted on Sep 25, 2020 5:54 PM

Hi, update time!

Just in case anyone is like me and scouring the web, looking at 10+ year old forum posts with a semi-working iMac G3 and stressing over what the problem could possibly be - after a LOT more messing about with swapping the hard drive, CD drive, extensive internal cleaning, completely new OS, etc, I finally solved the issue.

I reseated the first RAM chip, but poorly, and received a "RAM test failed" error on startup... However, it continued booting up and started working perfectly (for the very first time!) So I reseated it once more, making sure the contacts were clean and it was properly in place, booted again, and received an impassable "Unimplemented trap" error. Hmm. Similar to my original problem.

I then thought of the possibility that it could just be bad RAM, so I removed the stick entirely and it booted fully, 0 problems, 0 errors, albeit with half the RAM. Finally an end to my stressful quest!!

I plan to buy a replacement RAM stick, but in the meantime I'm finally able to sit down and use it properly, and I'm thankful. At now it's all cleaned up! Thanks Jan for your assistance.

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Noje999 Author

Level 1

4 points

Sep 25, 2020 5:54 PM in response to Noje999

Hi, update time!

I plan to buy a replacement RAM stick, but in the meantime I'm finally able to sit down and use it properly, and I'm thankful. At now it's all cleaned up! Thanks Jan for your assistance.

Jan Hedlund

Level 7

24,235 points

Aug 29, 2020 3:45 AM in response to Noje999

Hi,

First of all, would it be correct to assume that the 8.6 install disc in question is either a generic retail CD or a system disc for exactly this iMac model? That is, not an 8.6 system CD for any other Mac?

No problem when using the 8.6 installer?

Since the iMac successfully boots with extensions off, one would normally have suspected some kind of problem with the operating system.

I guess that you have tested a PRAM reset already.

The PEOF problem may be unrelated. Reformatting the drive, as you have done, should have corrected that issue. At this point, you could of course use yet another disk utility in order to completely wipe and reformat the drive. If you have access to a Linux or Windows PC, you may even want to wipe/reformat the hard drive there, and then repeat the process in the iMac with proper Mac utilities.

Noje999 Author

Level 1

4 points

Aug 29, 2020 9:29 AM in response to Jan Hedlund

Hi, thank you for your response - the Macos 8.6 disc is one that I created myself from an ISO on a modern OSX system. There were no issues booting from and installing the os, which I've done a couple times now just to be sure, but still getting the same 'illegal instruction' error as before when I first got the machine from the previous owner. They said this error first came up after leaving this computer in the loft for 15 years, so I'm thinking its possibly a hardware issue since I've tried formatting the disk multiple times.

I shall try again though! Maybe I'll try installing os9 to see if that changes anything at all.

And yes, I have tried the 3x PRAM reset.

Noje999 Author

Level 1

4 points

Aug 28, 2020 5:27 PM in response to Noje999

Minor correction, I used a mac os 8.6 install disc (not 8.9)

Jan Hedlund

Level 7

24,235 points

Sep 25, 2020 9:46 PM in response to Noje999

Hello,

Thanks for the update. Glad to hear that you solved the problem, and that the computer is working as it should.

Regards,

Jan

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iMac G3 333MHz Tray-Loading: Boot issue?