Open Firmware, now also known as OpenBIOS, is hardware-independent firmware (computer software which loads the operating system) initially developed by Sun Microsystems for use in their SPARC-based workstations and servers. It was described in IEEE 1275 and adopted by PowerPC-based systems such as PegasosPPC. However, IEEE 1275-1994 was not affirmed by the Open Firmware Working Group in 1998 and has since been withdrawn.[1][2]
Open Firmware may be accessed through its command-line interface, which is based on the Forth programming language.[2]
Apple and Open Firmware[]
Apple Computer adopted Open Firmware with its PCI-based Power Macintosh models, starting with the Power Macintosh 9500 in 1995. For such models through the beige Power Macintosh G3, the classic Macintosh Toolbox was stored within the boot ROM itself as an Open Firmware device. Thus, they are still classified as Old World ROM systems. Starting with the first iMac G3 in 1998, a bootloader would instead load New World ROMs from the boot drive. The Open Firmware interface can be accessed at startup by holding down the COMMAND + OPTION + O + F keys.[3][4]
Booting[]
Open Firmware on PowerPC Macs can boot from a drive volume partitioned through an Apple Partition Map (APM). However, it is unable to support booting from drives partitioned through a GUID Partition Table (GPT) favored by Intel-based Macs, though such volumes can be mounted and accessed.[5]
Version history[]
Open Firmware versions are not indicative of release order as Apple tended to release newer firnware in portable PowerPC notebooks than desktop models.[4][6] Some firmware updates were released with a confusing naming convention where it was unclear whether the number referred to the version of the update itself or the resulting firmware version after the update.[7]
| Version | Models | Startup icon | Notes |
|---|---|---|---|
| 1.0.5 | Power Macintosh 7200, 7300 to 9600 | Monochrome | First released in 1995.[4] |
| 1.1.22 | Apple Network Server 500, 700 | n/a | No Mac OS booting.[4] |
| 2.0 | Power Macintosh 5400, 6360, 6400 | Monochrome | |
| 2.0f1 | Power Macintosh G3 (beige, rev.A) | Color | |
| 2.0.1 | PowerBook 2400c, 3400c, PowerBook G3 (Kanga, Wallstreet, PDQ) | Color | |
| 2.0.2 | Power Macintosh 4400/7220 | Color | |
| 2.0.3 | Power Macintosh 5500, 6500, 20th Anniversary Macintosh | Color | |
| 2.4 | Power Macintosh G3 (beige, rev.B and later) | Color | |
| 3.x | iMac G3 (tray loading), Power Mac G3 (B&W), PowerBook G3 Series (Lombard) | Color | New World ROMs, updatable.[4] |
| 4.1.7 | iBook G3 (clamshell) | Color | Firmware update[7] |
| 4.1.8 | PowerBook G3 Series (Pismo, 2000), Power Mac G4 (Digital Audio, 2001) | Color | Firmware update[7] |
| 4.1.9 | iMac G3 (slot loading), Power Mac G4 Cube | Color | Firmware update[7] |
| 4.2.0 | iBook G3 (Dual USB, 2001) | Color | No USB disk (UD) booting.[6] |
| 4.2.8 | Power Macintosh G4 (Sawtooth) | Color | Firmware update[7] |
| 4.2.9 | PowerBook G4 (550 - 667 MHz) | Color | Firmware update[7] |
| 4.4.8 | Power Mac G4 (Mirror Drive Doors, 2003) | Color | |
| 4.8.6 | PowerBook G4 (2004) | Color | |
| 4.8.9 | Mac mini G4 (2005) | Color | |
| 4.9.0 | PowerBook G4 (12", 2005) | Color | Boot picker support.[6] |
| 4.9.1 | PowerBook G4 (17", 2005) | Color | |
| 4.9.3 | iBook G4 (2005) | Color | |
| 5.1.4 | Power Mac G5 (2003) | Color | Firmware update[7] |
| 5.1.5f2 | Power Mac G5 (single processor, 2003) | Color | Firmware update[7] |
| 5.2.7 | Power Mac G5 (2005) | Color |
Discontinuation[]
Starting in 2006, Apple phased out its use of Open Firmware in favor of EFI (Extensible Firmware Interface) during its transition to Intel processors.[4]
References[]
- ↑ IEEE Standard for Boot (Initialization Configuration) Firmware: Core Requirements and Practices, Institute of Electrical and Electronics Engineers. 1994.
- ↑ 2.0 2.1 That same Open Firmware Forth system by DonHopkins, Y Hacker News. 2015-07-07.
- ↑ A guide to Open Firmware - The Apple BIOS by linuxopjemac, iLinux. 2010-02-06. Archived 2010-05-23.
- ↑ 4.0 4.1 4.2 4.3 4.4 4.5 NetBSD/macppc Model Support, NetBSD. Accessed 2021-03-04.
- ↑ Open Firmware Macs cannot boot from GPT partitioned disks by komakino, Ars Technica OpenForum. 2005-03-31.
- ↑ 6.0 6.1 6.2 The Open Firmware Wiki by z970, MacRumors. 2020-02-28.
- ↑ 7.0 7.1 7.2 7.3 7.4 7.5 7.6 7.7 PowerPC Mac Firmware / Boot ROM Updates by AphoticD, MacRumors. 2021-02-23.
See also[]
External links[]
- Technical Note 1061: Fundamentals of Open Firmware, Part I at Apple Developer Connection (2000-06-01, mirrored)
- Technical Note 1062: Fundamentals of Open Firmware, Part II (1996-09-01, mirrored)
- Technical Note 1044: Fundamentals of Open Firmware, Part III (2001-06-26, mirrored)
- FirmWorks The Open Firmware Source
- Hardware Independent Boot Code: Open Firmware by M.E. Johnson at Sabaki Engineering (1996, archived 1997-05-02)
- The Open Firmware Wiki by z970mp at MacRumors (2020-02-28)
- Open Firmware at GitHub
- Open Firmware at MorphOS Library
- Open Firmware at the OLPC Wiki
- Open Firmware at OpenBIOS
- Open Firmware at Wikipedia
