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Mac os 8.6 open firmware user manual
Mac os 8.6 open firmware user manual








If the auto-boot? variable is flagged as false, the system will halt the boot process and drop to the Open Firmware user interface. If additional information is required the boot-file variable is read. If the auto-boot? variable is flagged as true, the system will then read the value contained within the boot-device variable and attempt to boot from that device. Open Firmware will then probe the system's I/O buses to determine the device configuration and build a device tree, which describes the hardware it has located, the system will then examine the values of its enviroment variables. When enough initialization has occurred to execute Open Firmware, the boot chime is played and Open Firmware is loaded. With the new family of iMac systems, additional pre-firmware diagnostics are performed due to the addition of the UniNorth and KeyLargo ICs.

MAC OS 8.6 OPEN FIRMWARE USER MANUAL CODE

These POST tests are run in native PowerPC code and involve checksum testing, memory testing, detection of the manufacturing test pin and test manager support. The boot ROM stored in NVRAM provides power on self test (POST - diagnostics), and initializes enough of the system to load Open Firmware. The boot process starts with the PowerPC processor executing its reset vector as specified by the Hardware Initialization code. Open Firmware is pretty easy to access and navigate once you know how, this guide walks you through the basics, so you can get to know your system a little better. Open Firmware acts as a type of bios for the PowerPC system, it is responsible for identifying various hardware components and uses a series of environment variables to all the user or developer to modify the boot behavior of the system. These machiens are normally referred to as "NewWorld Macs". Most Apple G3/G4 systems use a modified version of the Open Firmware standard. A guide to Open Firmware - The Apple BIOS








Mac os 8.6 open firmware user manual