[Andrew Stephens]

Does anyone have any info as to what may be going wrong at each stage that OS X fails to boot a Mac.

for instance the worst case would be the flashing no system icon meaning that things are so hosed that the mac can't even recognise a valid OS

but what if the Mac gets as far as the grey apple logo, or the spinning gear, or maybe the blue screen after the OS X bar but before the finder kicks in.

Any info on what services go wrong where would be very interesting.

[hookem2oo7]

start up in verbose mode (hold cmd + v at the chime) to get more detailed information.

[Andrew Stephens]

Originally Posted by hookem2oo7 

start up in verbose mode (hold cmd + v at the chime) to get more detailed information.

True. Iwas thnking of a quick guide to each staeg. So far I have:

No system: no system installed, no drive/failed drive

Hangs at grey screen pre apple logo: Kernal fails to load

Hangs at blue screen after spinning gear: Login app fails to load

But there must be a few more stages.

[JKT]

Do a search for starting up in Mac Help - there are a few things listed there as to what can go wrong.

I don't know if new Macs still do this, but there is/was one preceding the flashing question mark, which was the sound of a car crashing and glass breaking (due to bad RAM, IIRC).

[Art Vandelay]

Originally Posted by JKT 

I don't know if new Macs still do this, but there is/was one preceding the flashing question mark, which was the sound of a car crashing and glass breaking (due to bad RAM, IIRC).

It's probably been over a decade since they've done that. IIRC, it was the first gen PowerPC Macs that did that. Current Macs will emit tones if there is a problem. Based on the tones, you can diagnose the problem.