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Find missing FireWire devices
Holding Cmd+Opt+P+R will not perform as noted in this hint. When held, that particular key combination will continually reboot your Mac until you release it.
Clearing P-RAM and resetting the PMU are different
Macs' 'Parameter-RAM' and 'NonVolatle-RAM' are like a preferences files in firmware. Clearing the P-RAM is useful only when there is something corrupt written to this battery backed RAM. Holding down Apple+Option+P+R on boot will reset the P-RAM, and sometimes fix strange behavior such as failure to find the startup volume. P-RAM was used more extensively under Classic OS 9, and therefore was a primary troubleshooting step.
Clearing P-RAM and resetting the PMU are different
Just to fill in some fun backstory from WWDC this year...
Clearing P-RAM and resetting the PMU are different
Just to fill in some fun backstory from WWDC this year...
Why the reboot loop
When the machine starts up, the boot code (in the OpenFirmware) looks at the keyboard and looks for certain combinations. If it sees Cmd, Opt, P, and R all pressed, it jumps to a routine which (1) resets the PRAM, (2) plays the three tones, and (3) resets the machine. |
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