Apple Desktop Computer Bedienungsanleitung PDF herunterladen (Seite 61)

CHAPTER 5

Software

Boot ROM Contents 61

Failure to boot in POST causes the error beep, optionally entering the

Mini-Nub.

Open Firmware 5

The Open Firmware component of NewWorld is based on the CHRP version of

Open Firmware, also known as Open Firmware 3.0. This is the most robust and

full-featured Open Firmware used by Apple to date. This version of Open

Firmware contains several notable changes from the Open Firmware found in

the ﬁrst and second generation PCI Macintosh computers:

■ Open Firmware is capable of reliably reading ﬁles from block devices.

■ Open Firmware builds an expanded device tree that holds every facet of

hardware information needed by an operating system.

■ Open Firmware contains code that mimics the StartSearch code in the

ToolBox ROM and provides a Mac-like user interface during startup.

■ Open Firmware creates an interrupt tree that is interlaced through the Device

Tree to provide a mechanism to describe the interrupt layout of the

computer.

If a boot failure occurs in Open Firmware, Open Firmware attempts to provide

a Macintosh-like experience.

Mac OS 'ndrv' Drivers 5

The Boot ROM may also contain Mac OS drivers that are hardware-speciﬁc and

needed at boot time; they are organized as 'ndrv' drivers. Drivers needed at

boot time (video drivers, network drivers, or disk drivers) need to be loaded

from the Device Tree.

RTAS 5

RTAS (Run-Time Abstraction Services) can be thought of as a BIOS. RTAS code

handles hardware accesses needed by an OS, making it possible for multiple

operating systems to get hardware services without having to know the

speciﬁcs. RTAS handles hardware-speciﬁc services such as NV-RAM

(containing parameter RAM), time services (the real time clock), PCI

conﬁguration cycles, power management, and the code needed to restart and

shutdown.

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Apple Desktop Computer Bedienungsanleitung Seite 61