PowerMac G4 Digital Audio 2001 - Continuously showing "bus error" at boot

[viksn0w]

Hi,
I restored some months ago my PowerMac G4, but now a new problem showed up: "bus error". At every boot this error shows up. I reinstalled the OS so many times that I lost the count. Usually when I reinstall the OS, this error shows up after 5 powers off or sometimes I install the OS, the Finder crashes continuously with a massage "Finder quitted unexpectedly - It's better to restart the machine", I restart the Mac and "bus error" shows up. Sometimes the error comes up also at a CD boot attempt and always sometimes the "bus error" disappears after opening the case of the PowerMac and connect-disconnect cables. Does someone of you have the same issue?

[FdB]

https://discussions.apple.com/thread/304622

[viksn0w]

The link that you sent doesn't exist is closed

[Philgood]

I experienced a lot of changing in Apple's website so maybe best practice to copy the text over to preserve it for future generations.

Here it goes...

Bus and address errors occur when a segment of memory is inaccessible -- either because it is reserved for another use or it doesn't exist. These are the most common system errors and are likely caused by an extension conflict, insufficient memory, or corruption in an application or an application's support file (e.g., a preferences file).
 

 
Other causes could include faulty application code, or a bad logic board. Because these causes are less likely causes, you should for them only after troubleshooting for the most common causes.
 

 
Possible Solutions: When either of these errors occur in only one application, try running the application with extensions disabled. If the error does not recur, troubleshoot for extension conflicts.
 

https://web.archive.org/web/20071014044414/http://docs.info.apple.com/article.html?artnum=30929 Mac OS: Extension Conflict Troubleshooting/Extensions Manager Features.
 

 
If the error occurs in only one application and while extensions are disabled, try trashing the application's preferences file so the application creates a new one. If the error does not recur, a damaged preferences file was the cause.
 
Preferences are found inside the Preferences Folder which is located inside the System Folder.
 

 
You should also try allocating more memory (RAM) to the application.
 

https://web.archive.org/web/20080127093547/http://docs.info.apple.com/article.html?artnum=18278  Mac OS: Assigning More Memory to an Application Program. The same directions are also in the OS Mac Help Menu.
 

 
If the error occurs in more than one application, the cause may be a problem with either the system software or, perhaps, the hardware. Reinstalling your system software will likely resolve errors caused by damaged system software. If the error is caused by hardware, SCSI devices attached to your Macintosh may be the cause and you should troubleshoot the SCSI chain.
 

 (The last sentence does not pertain to your iMac)

[FdB]

"so may be best practice to copy the text over to preserve it for future generations"

Yes, thanks Philgood. I was surprised to even find that concerning a G4... still on Apple's site.
And then to hear that the link didn't work. (It did require two attempts to get there today.)

Thank you.

[viksn0w]

Thanks Philgood! 
I'm going to try it now!

[viksn0w]

Ok, I tried and this is the result
I don’t know what to do 

[viksn0w]

I also checked the RAM and it is ok. So I'm kinda confused

[FdB]

So…

You’re cold-booting (from machine completely off state) and holding down the shift key while pressing the power-on button… and holding down that shift key until after the above-pictured opening screen appears… and it still reports the bus error?

If so, have you tried *booting from the machine’s original OS install-disks OR the 9.2.2 installer disk available here while trying any / all of the following?

*Holding down the C-Key with the installer disk in the drive.
 Holding down the Option-key with the install disk in the drive
 Holding down the Option-key + Cmd-key + the O-key + the F-key to try Open Firmware boot?

Have you attempted to rebuild your desktop / Zap the PRAM?
(Option + Cmd + P + R) allowing the machine to “chime” at least three times before releasing?

If it boots from an install disk and is stable… then you might have a drive problem (with that IBM HD). And we are talking about the Quicksilver (2000 - you now note 2001) that you got back in February... or is this a different G4?

OR try (as DH is probably going to comment) running / booting with Apple Hardware Test to run complete diagnostics on the machine… if this is possible?

If you’ve just been “restoring” your OS and not doing a complete re-install (wipe, reformat and fresh driver update) you might be suffering from some previously installed “gremlin”. All unnecessary cards and / or other “accessories” disconnected while you attempt all of this?

Blow the machine out, remove - clean and reseat all the RAM and check the main internal connection to the motherboard from the Power Supply.

However, if the machine was stable just months before now… some-thing may be going “haywire”. What changes have you made to the machine since you got it?

[refinery]

I also checked the RAM and it is ok. So I'm kinda confused

how exactly did you go about doing this?
personally I would think this is the most likely culprit, failing RAM. It may test fine now... and work fine... until it doesnt. RAM can be very elusive that way.
if you have more than one stick, I would try taking them out one at a time and see if the problem stops at some point.

[IIO]

regardless what apple said on this old website a bus error in my experience can be anything with hardware buses, not only RAM.

[FdB]

If it only occasionally throws the error message even with a CD boot… but disappears after disconnection / re-connection of “cables” - I’d be looking pretty closely at those individual wires for scrapes, abrasions and possibly un-seen, weakened interior break points in those wires and where those “cables” are connected. Really beginning to sound more like an intermittent-connect, wiring problem.

Repeated opening and closing of that door and possibly the occasional pinching of wires…

Boot it with the door only open first, if that gives the error msg. then try it again with the door open while slightly holding-up (applying some slight tension to the wiring harness) and maybe even try tension in various directions.

OR, does it boot stable with just the door open?