Executive Summary of the
Non Volatile Memory Chips Inside Apple Computers.
Commonly known as "NVRAM" chips.
Generally speaking, this type of ram is equivalent to the nvRAM the BIOS uses in a IBM-PC type computer to save the time and date.
The "Open Firmware" chip in a Apple, and again generally speaking, is equivalent the the BIOS chip like the Phoenix or AMI chip used in a IBM-PC type computers.
Understanding this type of memory is often confusing in Apple computers, especially in their laptops.
Going to the Apple support website and others does not help, and will get you even more confused!!!
The two types of nvRAM are:
The "Parameter Random Access Memory" or pRAM:
Stores the information "Open Firmware" uses.
It is managed via the /usr/sbin/nvram terminal command.
The use of the nvram terminal command, is why it is often referred to as NVRAM incorrectly !
The Power Management Unit or PMU and the System Management Controller or SMC.
Both perform similar functions, but are called different names depending on what CPU type you have.
The PMU, is used on the older PPC (PowerPC) based computers.
And the SMC, is used on the newer INTEL based computers.
And a THIRD type is often included, but is not RAM at all.
(It's kinda sorta like a secret disk partition)
Is called rEFIt or EFI...
For more specific information, please see my detailed page.
