User:Atyndall/AIP/BootX

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Reviewed version: May 25, 2008
BootX
70px
Image:BootX.png
BootX booting screen found on any Macintosh running Mac OS X 10.2 or later
Developed by Apple Inc.
Initial release August 24, 2002 (with Mac OS X 10.2) [1][2]
OS Darwin & Mac OS X [3]
Platform PowerPC [4]
Development status Active
Genre Boot loader
License Apple Public Source License [5]

BootX is a software based boot loader created by Apple Inc. for use in it's Macintosh computer range, it is used to load all required device drivers and boot the Mac OS X kernel [6] on all PowerPC Macintoshes [4] running Mac OS X 10.2 or above [2].

Using BootROM, a read-only memory computer chip containing OpenFirmware, it's graphical frontend is shown briefly on all compatible Macintosh computers as a grey Apple logo with a spinning cursor that appears during the startup sequence [7]. It is released as part of the Darwin operating system under the open source Apple Public Source License [5] and was superseded by boot.efi and an Extensible Firmware Interface ROM on the release of the Intel-based Mac [4].

Contents

[edit] Features

Mac OS X booting up in Verbose Mode
Mac OS X booting up in Verbose Mode

To make the boot loader appealing to other operating system developers Apple added many features to the boot loader to allow flexibility in the booting process. As well as being able to boot from HFS, HFS+, UFS and ext2 formatted volumes, it can network boot using TFTP and load Mach-O and ELF kernels [8].

The bootloader can be manipulated at startup by holding down various key combinations to alter the booting process. Such functions include Verbose Mode, achieved by holding down the Command and V key at startup, which replaces the default Apple logo with Unix boot messages and Single User Mode, achieved by holding down the Command and S, which, depending on the operating system, may boot into a more basic command-line version of the operating system, to facilitate maintenance and recovery action [9]. It can also be set to disallow access to these technical functions using the OpenFirmware interface [10].


[edit] Boot process

In the PowerPC Macintosh the boot process starts with the activation of BootROM; the basic Macintosh ROM, which performs a Power On Self Test; testing hardware essential to startup [4]. On the passing of this test control of the computer is passed to OpenFirmware. OpenFirmware initializes the Random Access Memory, Memory Management Unit and hardware necessary for the ROM's operation. It then checks settings, stored in NVRAM, and builds a list of all devices on a device tree by gathering their stored FCode information. Once this is completed, control switches from the ROM to the Harddrive and BootX is started [6].

BootX then configures the keyboard and display, claims memory for various purposes and checks to see if various key combinations are being pressed [7]. After this has been completed BootX displays the grey apple logo and precedes to load the kernel, CoreGraphics and the user interface (WindowServer) [11].

[edit] History

thumb|Old World boot icon The older Macintoshes (1983-1998) utilized a very basic bootloader, it was solely a ROM chip varying in sizes up to 4 megabytes [12], which contained both the computer code to boot the computer and to run Mac OS. This was known as the Macintosh Toolbox, or the Old World ROM and was used in all Macintosh computers up until mid-1998 [13].

thumb|New World boot icon|left With the advent of the iMac and Mac OS 9 in 1999 [14] the firmware received a massive update, the ROM was reduced in size to 2 megabyte, christened BootROM, and the remainder of the ROM was moved to the file Mac OS ROM in the OS 9 System Folder [13]. It used a full implementation of the OpenFirmware standard (contained in BootROM) and was nicknamed the New World ROM [15]. This saw the introduction of the full color "Happy Mac" icon.

In 2002, with the release of Mac OS X 10.2, the Mac OS ROM file was replaced with the BootX bootloader file [13], the historical "Happy Mac" icon was replaced with a grey apple logo [16].

With the introduction of the Intel Mac in 2006 [17], BootROM was replaced by the Extensible Firmware Interface ROM and the boot.efi file [4].

[edit] Notes

  1. ^ Jaguar “Unleashed” at 10:20 p.m. Tonight (HTML). Apple Inc. (2002-08-23). Retrieved on 2008-05-02.
  2. ^ a b Siracusa, John (2002-09-05). Mac OS X 10.2 Jaguar (HTML) pp. 3. Ars Technica. Retrieved on 2008-05-03.
  3. ^ Darwin 9.2 Source Code (HTML). Apple Inc.. Retrieved on 2008-05-17.
  4. ^ a b c d e System Startup Programming Topics: The Boot Process (HTML). Apple Inc. (2007-02-08). Retrieved on 2008-05-01.
  5. ^ a b Apple Public Source License (HTML). Apple Inc. (2003-08-06). Retrieved on 2008-05-02.
  6. ^ a b Singh, Amit [2006]. "The Firmware and the Bootloader", Mac OS X Internals: A Systems Approach (HTML), Addison-Wesley, pp. 324-325. ISBN 0321278542. Retrieved on 2008-05-03. 
  7. ^ a b Singh, Amit. Booting Mac OS X (HTML). kernelthread.com. Retrieved on 2008-05-01.
  8. ^ Gerbarg, Louis. BootX: The Mac OS X Bootloader (PDF) pp. 7-8. Rensselaer Polytechnic Institute - Computer Science Department. Retrieved on 2008-05-01.
  9. ^ Mac OS X keyboard shortcuts (HTML). Apple Inc. (2007-10-17). Retrieved on 2008-05-02.
  10. ^ Setting up firmware password protection in Mac OS X (HTML). Apple Inc.. Retrieved on 2008-05-03.
  11. ^ Singh, Amit. Mac OS X System Startup (HTML). kernelthread.com. Retrieved on 2008-05-15.
  12. ^ Macintosh: ROM Size for Various Models (HTML). Apple Inc. (2000-08-23). Retrieved on 2008-05-15.
  13. ^ a b c Singh, Amit [2006]. "The Firmware and the Bootloader", Mac OS X Internals: A Systems Approach (HTML), Addison-Wesley, pp. 267-268. ISBN 0321278542. Retrieved on 2008-05-03. 
  14. ^ Apple Announces Mac OS 9: The Best Internet OS Ever (HTML). Apple Inc. (1999-10-05). Retrieved on 2008-05-17.
  15. ^ The Macintosh ROM and The NewWorld Architecture (HTML). Apple Inc. (1999-03-26). Retrieved on 2008-05-15.
  16. ^ Markoff, John. "Compressed Data; Happy Mac Becomes an Icon of the Past" (HTML), The New York Times, 2002-08-26. Retrieved on 2008-05-17. 
  17. ^ Apple Unveils New iMac with Intel Core Duo Processor (HTML). Apple Inc. (2006-01-10). Retrieved on 2008-05-16.

[edit] See Also

[edit] External Links


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