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Power Macintosh computers that support the PCI bus contain nonvolatile RAM (NVRAM) chips with a minimum capacity of 4 KB. A typical allocation of NVRAM space is described in Typical NVRAM Structure.
An important use of the Power Macintosh NVRAM is to store the little-endian? variable, discussed in Addressing Mode Determination.
In Macintosh computers that support the New World architecture, hard-coded offsets to locations in NVRAM for Mac OS PRAM variables are no longer used in the same way. Instead, NVRAM is divided into variable-sized partitions that are available to the Mac OS, Open Firmware, or any other client. This partitioning scheme is based on the Common Hardware Reference Platform (CHRP) specification.
Mac OS PRAM variables reside in the Mac OS partition in NVRAM, and API calls to modify PRAM refer to offsets within the Mac OS partition. The Mac OS also stores device configuration properties in NVRAM that are used by Open Firmware at startup time. These properties are stored in an Open Firmware config variable. The Mac OS uses Name Registry functions to load this information into NVRAM to provide device boot-time configuration services for Open Firmware drivers and Mac OS drivers during subsequent startup of the system.
See, Introduction to the NewWorld Architecture for a discussion of the significant software changes implemented in the New World architecture.