Panic.log - What is this?

Question

I was looking at my Console logs and found this panic.log shown below. I had walked away from my iBook G4 running 10.3.9 and when I came back everything was dark: not sleeping and not "display off"
I pressed the power switch and it rebooted OK. I went to Console to see if there were any hints. There was a panic.log file:
Mon Mar 26 12:19:00 2007
panic(cpu 0): Uncorrectable machine check: pc = 000000000063EB30, msr = 0000000000149030, dsisr = 40000000, dar = 000000000030E88C
AsyncSrc = 0000000000000000, CoreFIR = 0000000000000000
L2FIR = 0000000000000000, BusFir = 0000000000000000
Latest stack backtrace for cpu 0:
Backtrace:
0x00083498 0x0008397C 0x0001EDA4 0x0009160C 0x000908F8 0x0009402C
Proceeding back via exception chain:
Exception state (sv=0x25744500)
PC=0x0063EB30; MSR=0x00149030; DAR=0x0030E88C; DSISR=0x40000000; LR=0x00555E24; R1=0x12243C00; XCP=0x00000008 (0x200 - Machine check)
Backtrace:
0x00256268 0x00569B6C 0x00568DC0 0x0056CA54 0x0056CD64 0x0056CB78 0x00035148 0x00035028
Kernel loadable modules in backtrace (with dependencies):
com.apple.driver.AppleUSBHub(2.1.5)@0x566000
dependency: com.apple.iokit.IOUSBFamily(2.1.5)@0x54a000
Exception state (sv=0x25744280)
PC=0x00000000; MSR=0x0000D030; DAR=0x00000000; DSISR=0x00000000; LR=0x00000000; R1=0x00000000; XCP=0x00000000 (Unknown)
Kernel version:
Darwin Kernel Version 7.9.0:
Wed Mar 30 20:11:17 PST 2005; root:xnu/xnu-517.12.7.obj~1/RELEASE_PPC
What does it mean and what can I do about it?
TIA,
Roberto
iBook G4 Mac OS X (10.3.9)

Answer 1

Hi Roberto,
> Don't want to leave this question just hanging...
   ... but you did. You haven't added any new information. You won't learn any more about the panic from the panic log alone. William is by far the best at reading panic logs of anyone ever to have graced this list. He has actually contributed code to Darwin's kernel. I was thrilled that he posted on this thread because he is probably familiar with the code that throws a Machine Check error. He has indicated the it probably came from your USB driver or the memory controller.
   You should be able to test your RAM with the hardware test disk that came with your computer. If that test shows no problems then you've probably connected a device to your computer via USB that is misbehaving. If a panic occurs every time you plug in a particular device then the culprit is obvious but if the panic hasn't reoccurred then it's unlikely that you'll ever find out exactly what happen this time.
Gary
~~~~
   Well, don't worry about it... It's nothing.
         -- Lieutenant Kermit Tyler (Duty Officer of Shafter Information
               Center, Hawaii), upon being informed that Private Joseph
               Lockard had picked up a radar signal of what appeared to be
               at least 50 planes soaring toward Oahu at almost 180 miles
               per hour, December 7, 1941.