Can't help you fully, but if I get into diagnosing hardware problems I do the following:
Remove all 3rd party hardware devices (PCI cards, ext. FireWire and USB stuff) etc. Also remove 3rd party RAM...
(Re)Boot the Mac in OpenFirmware (press and hold < COMMAND >, < OPTION >, < O >, < F >).
Type:
- reset-nvram < ENTER >
- set-defaults < ENTER >
- reset-all < ENTER > (will now reboot automatically)
Start with < SHIFT > pressed (safe-boot)
Download and use
Rember (GUI - memtest), and do the full test (will take some time, depends on how much RAM is installed).
Also, (Re)Boot in "verbose mode" (Boot while pressing and holding < COMMAND >, < V >), and try to notice any out-of-the-ordinary messages...
Maybe some external FW Disk with a known-good Mac OS X boot system could help you out too?
Sorry, I don't have any links to "real" hardware test CD's, but this type of diagnoses usually helps me isolate the problem.
Other advise (if physically possible):
- swap the Boot disk (check to see if no problems occur in another comparible Mac)
- Insert a new HD, and install a brand new Mac OS X
- Avoid using ADC. Sometimes using only DVI (or VGA) instead of ADC on the grfx card can eliminate problems
- Boot into Target Disk Mode (Re)Boot while pressing and holding < T >.
If this does work, but normal boot does not, you can at least backup the drive (connect to another Mac using a FireWire cable), and check to see that OF still is alive, and so is the disk.
- Grab a beer, and call it a day.
Good luck, m8.
