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As explained in Startup and System Configuration PCI expansion cards in Power Macintosh computers may need to operate during the Open Firmware startup process, before any operating system is present. The drivers for such cards are called Open Firmware drivers. Other drivers, called run-time drivers, are used only after an operating system has been loaded and has taken control of the main processor. Read Open Firmware FCode Options, for help in deciding whether or not your PCI card needs an Open Firmware driver.
This chapter discusses the general technical requirements for Open Firmware drivers for PCI devices--drivers that are used with the Open Firmware startup process. Run-time drivers for PCI devices used with Mac OS and other operating systems are discussed in Part 3, Native Device Drivers