PATH ADC Home > Documentation > Hardware
> iBook Developer Note
|
The system software in the iBook uses the ROM-in-RAM approach also used in the iMac and the 1999 Power Macintosh G3 computer. With the ROM-in-RAM approach, also called the NewWorld design, a small ROM contains the code needed to initialize the hardware and load an operating system. The rest of the system code that formerly resided in ROM is loaded into RAM from disk or from the network.
The small ROM that is needed for the computer's start-up activities, called the boot ROM, is only 1 MB in size. It includes the hardware specific code and tables needed to start up the computer, to run Open Firmware, to provide common hardware access services, and to load the Mac OS ROM image.
High level software resides in an image called the Mac OS ROM that is read into RAM before the Mac OS begins operation. Once the Mac OS begins operation, the Mac OS ROM image in RAM behaves in the same way that the corresponding code in ROM formerly did. Most of the changes are completely transparent to the Mac OS.