is Parameter RAM which a non-volitile RAM chip that keeps various bits of information about the System Parameters(settings) stored between power downs.
Information like date, time, port settings, screen resolution, network settings and a bunch of other things. It is all kept running by the little 3.6 volt lithium battery that sits on the logic board. Usually the first noticeable indication that this battery is failing is that the date and time revert to a certain date. It used to be 1904, then 1956 and now it is some other date. Replacing the battery, resetting any of the settings that reverted to default, puts you back on track.
Occasionally the PRAM becomes corrupt and can prevent the machine from booting up. It's at this point that you ZAP the PRAM. All this does is erase certain parts of the information that is stored there, which forces the system to reload the PRAM with new, and uncorrupt, information and, hopefully, the machine will boot. Apple+Option+P+R will accomplish this. It is not a routine maintenance thing.
Does that help?
P
I keep seeing references to this PRAM thing. What is it? What does it accomplish?
Thanks

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