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Macintosh startup
View on WikipediaThe Macintosh startup sequence for Apple Macintosh (or Mac) computers includes hardware tests and diagnostics which can trigger the startup chimes and/or other instances of success or failure of the startup routines.
The startup sequence provides auditory and visual symbols of the computer's status and condition as it powers up, providing users with immediate feedback on the machine's soundness. Additionally, they allow the user to quickly identify any potential problems and take any appropriate actions to rectify faults.
Startup process
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Macs made from 1984 to 1998 used Old World ROM as the boot loader for all Macs produced around that time period. From 1998 up until the PowerPC to Intel transition, New World ROM was used for all Macs starting with the first iMac and later expanding to the first iBook and the Blue and White Power Mac G3. BootX is used as the boot loader for macOS on Old World/New World Macs. Most Intel-based Macs used Apple's implementation of UEFI as the boot loader, while those with a T2 security chip used a slightly different approach where it verifies the digital signature of the UEFI firmware via the security chip, which will then load the firmware upon successful verification.[1] All Apple silicon-based Macs use a newer method separate from previous Macs where it uses a boot ROM located on the SoC to launch iBoot, in a similar manner to that of the iPhone and iPad.[2]
In all instances, the startup chimes will be heard upon completion of the boot process (if successful), and a Happy Mac (or the Apple logo on newer versions) will be displayed on the screen to visually indicate that no hardware issues were found during the boot process.[3][4] On the other hand, a failure to do so will result in a different outcome where a different sound will be heard in place of the startup chime. This would either be the Chimes of Death (for most Old World ROM Macs made from 1987 to 1998)[5] or a series of simple beep codes (for Macs made from 1998 onwards).[6] In addition, a Sad Mac with either one or two lines of hexadecimal codes will be displayed on some Old World ROM machines to visually indicate a hardware issue during the boot process.[3]
All Macs made from 2016 to 2020 have the startup chimes disabled by default,[7] however, it was later re-enabled on those Macs running macOS Big Sur or later; this can be disabled by the user within System Preferences (Big Sur up to Monterey) or System Settings (Ventura and later).[8]
Startup chime
[edit]The Macintosh startup chime is played on power-up, before booting into an operating system. The sound indicates that diagnostic tests were run immediately at startup and have found no hardware or fundamental software problems.[9] The specific sound differs depending on the ROM, which greatly varies depending on Macintosh model. For models built prior to the introduction of the Power Macintosh in 1994, the failure of initial self-diagnostic tests results in a Sad Mac icon, an error code, and (later) the distinctive Chimes of Death sounds.
The startup chime used in the first three Macintosh models is a simple square-wave "beep" generated at 600 Hz that was programmed in software by Andy Hertzfeld, utilizing the computers' onboard MOS 6522 VIA chip.[10] All subsequent sounds after it are various chords. Software engineer Mark Lentczner used the Apple Sound Chip, his innovation of sound for the Macintosh, to play the C major fourth chord used in the Macintosh II that was programmed in software.[11] Variations of this sound were employed until Apple sound designer Jim Reekes created the startup chime used in the Quadra 700 through the Quadra 800.[12] Reekes said, "The startup sound was done in my home studio on a Korg Wavestation EX. It's a C major chord, played with both hands stretched out as wide as possible (with 3rd at the top, if I recall)."[12] He created the sound as he was annoyed with the tri-tone startup chimes because they were too associated with the death chimes and the computer crashes.[13] He recalls that Apple did not give him permission to change the sound and that he secretly snuck the sound into the computers with the help of engineers who were in charge of the ROM chips. When Apple discovered this, he refused to change it, using various claims in order to keep the sound intact.[14] He is also the creator of the iconic (or "earconic", as he calls it) "bong" startup chime used in most Macintoshes since the Quadra 840AV. It was created with multiple synthesizers, one of them being Reekes' Wavestation using a modified version of the "Sandman" preset and another being an Oberheim Matrix-6.[15] A slightly lower-pitched version of this chime is used in all PCI-based Power Macs until the iMac G3. On the other hand, the Macintosh LC, LC II, and Macintosh Classic II do not use the Reekes chime, instead using a software-programmed F major fifth chord that simply produces a "ding" sound. The first generation Power Macintosh computers also do not use the Reekes chime, instead using a chord strummed by jazz guitarist Stanley Jordan on an Ovation (sometimes incorrectly attributed as a Yamaha in some sources) steel-string acoustic guitar[12][16] using the finger tapping technique. Furthermore, the Power Macintosh 5200–6300 computers use a unique chime (excluding the 5400 and 5500, which uses the same "bong" chime used in all PCI-based Power Macs) that was composed on the Fairlight CMI, which is also used in television commercials for the Power Macintosh and PowerBook series from 1995 until 1998. The 20th Anniversary Macintosh uses another unique chime, which was also composed on a Korg Wavestation using a modified version of a preset found on one of its sound expansion cards.
The chime used for all Mac computers from 1998 to early 2016 is the same chime that was first introduced in the iMac G3. It was produced by pitch-shifting the 840AV's startup chime, making it an F-sharp major chord. Since 2012, the Mac startup chime has been a registered trademark in the United States,[17] and is also featured in the 2008 Pixar film WALL-E when the titular robot character is fully recharged by solar panels as well as in the 2007 Brad Paisley song "Online".[18]
Starting with the 2016 MacBook Pro, all new Macs were shipped without a startup chime, with the Macs silently booting when powered on.[7] The startup chime would later be added to these models (and all subsequent models since) with the release of macOS Big Sur in 2020, which can be enabled or disabled in System Preferences.[19] The new startup chime introduced with Big Sur is similar to the previous chime except it was pitch-shifted down one semitone, producing an F major chord instead of an F-sharp one. The sound mixing of the new startup chime is also noticeably different from that of the previous chime. Prior to Big Sur's release, a similar-sounding variant of this startup chime was used during the "Simplicity Shootout" commercial shown at the iMac G3's introduction in 1998. Initially, the new startup chime from Big Sur was only used on Intel-based Macs equipped with a T2 security chip, with most other Macs at the time (including older ones) still using the previous chime (even when upgraded to Big Sur prior to the 2020 Mojave and Catalina security updates). Eventually, the new startup chime was brought over to all older supported Macs starting with the macOS Big Sur 11.0.1 beta, and a firmware update included in the macOS Catalina 2020-001 Security Update and the macOS Mojave 2020-007 Security Update brought the new startup chime in Big Sur to all Macs that support Big Sur, including the Late 2013 iMac (despite not officially supported by Apple to run Big Sur).
Happy Mac and Apple logo
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A Happy Mac is the normal bootup (startup) icon of an Apple Macintosh computer running older versions of the Mac operating system. It was designed by Susan Kare in the 1980s, drawing inspiration from the design of the Compact Macintosh series and from the Batman character Two-Face.[10] The logo also shares some similarities to the faces of the 1934 painting Deux personnages (Two Characters) by Pablo Picasso and to the Bauhaus emblem.[20][21] The icon remained unchanged for many years until it and its related icons were updated to 8-bit color by Lauralee Alben in the 1990s.[22]
The Happy Mac indicates that booting has successfully begun, while a Sad Mac (along with a "Chimes of Death" melody or one or more beeps) indicates a hardware or software problem. When a Macintosh boots into the classic Mac OS (Mac OS 9 or lower), the system will play its startup chime, and the screen will turn gray. The Happy Mac icon will appear, followed by the "Welcome to Mac OS" splash screen (or the small "Welcome to Macintosh" window in System 7.5 and earlier), which underwent several stylistic changes, the other significant ones being the inclusion of extension icons appearing in the bottom left as well as a progress bar that was introduced in System 7.5. Mac OS 8.6 and later include the version number in the splash screen (for example, "Mac OS 9" in big black text).
On early Macs without an internal hard drive, the computer boots up to a point where it needs to load the operating system from a floppy disk. The Mac displays a floppy disk icon with a blinking question mark until the user inserts the correct disk.[23] In New World ROM Macs, a folder icon with a question mark that repeatedly changes to the Finder icon is shown if a System Folder or boot loader file cannot be found on the startup disk.
With the introduction of Mac OS X, the Happy Mac icon was retained for the two initial versions of the operating system, beginning with Mac OS X 10.0. A new Happy Mac was introduced in Mac OS X 10.1, which looked largely identical to that found in previous Classic Mac OS operating systems with some minor changes. This is also the last version of Mac OS as a whole (both Classic Mac OS and Mac OS X) to use the Happy Mac icon.
In 2002, with the release of version 10.2, the Happy Mac symbol was retired and replaced with the Apple logo. Also, in addition to the blinking system folder icon, a prohibition icon was added to show an incorrect OS version is found.[24] In OS X Lion 10.7, the Apple logo was slightly shrunk and added a drop-in shadow.
In OS X Yosemite 10.10, the white screen with a gray Apple logo was replaced with a black screen with a white Apple logo, and the throbber was replaced with a progress bar, requiring a firmware update to be applied. However, this only applies to Macs from 2013 and later, including the 2012 Retina MacBook Pros,[25] with models released in 2012 or earlier retaining the previous white screen (with the progress bar instead of the throbber). The shadow on the Apple logo was removed in OS X El Capitan 10.11 (for 2012 and earlier Macs). In 2016 and later Macs (excluding the Early 2016 MacBook), the Apple logo appears as soon as the screen turns on rather than after the startup chime. The progress bar below the Apple logo would later be slightly moved to near the bottom of the screen starting with macOS Sonoma 14.
The design of the Happy Mac was reused as the icon for Face ID, introduced in iOS 11 for iPhone and iOS 12 for iPad.[26]
Bomb screen and kernel panic
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A bomb screen was an error message used in the Classic Mac OS operating systems in the event of a software error. It was first used in the initial version of Classic Mac OS used in the original Macintosh in 1984,[27] displaying a reason for the crash alongside a corresponding error code. Starting with System 7 in 1991, it was changed to be a standard error message if it believed it could manage the recovery process, resulting in the forced termination of the application. An accompanying error code is no longer present in this iteration, and in its place was the name of the error that caused the issue to occur. This iteration would be used for all versions of Classic Mac OS up to Mac OS 9.2.2, the last version of the Classic Mac OS operating system. In all instances, the "Restart" button would be present, which would allow the user to restart the computer from the operating system as the bomb screen typically locks out the user from any further use of the operating system. Oftentimes the computer would freeze after the restart button was pressed, forcing the user to hard reset the computer (many Mac users of the time would often keep a paper clip nearby alongside the computer for the same reason).
Starting with the release of Mac OS X (now macOS) in 2001, the old "bomb screen" error messages that were found in the Classic Mac OS operating systems were replaced with a kernel panic, which is a fatal system error screen that is initiated by the operating system's kernel upon reaching a critical system error. Kernel panics in macOS initially started off as a conventional Unix-style panic notification in Mac OS X 10.0[28] before switching into a small error message box in Mac OS X Jaguar that provides a multilingual alert to the user, indicating that the computer needs to be restarted.[29] The color for the kernel panic box was initially white in Mac OS X Jaguar, but was changed to black in Mac OS X Panther. In some rare instances, a Unix-style kernel panic would also be displayed with or without the kernel panic warning message. Starting with OS X Mountain Lion, the kernel panic was changed from a static box to a full-screen message, and can only be seen when the computer resets after a kernel panic has been encountered. The kernel panic message can be skipped. If there are five kernel panics occurring within three minutes after the first one, a prohibitory sign would be displayed for a few seconds before the computer shuts down afterwards. This phenomenon is known as a "recurring kernel panic".
Sad Mac
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A Sad Mac is a symbol in older-generation Apple Macintosh computers (hardware using the Old World ROM and not Open Firmware, which are those predating onboard USB), starting with the original 128K Macintosh and ending with the last NuBus-based Power Macintosh models (including the first-generation 6100, 7100, 8100, as well as the PowerBook 5300 and 1400),[30] to indicate a severe hardware or software problem that prevented startup from occurring successfully. The Sad Mac icon is displayed, along with a set of hexadecimal codes that indicate the type of problem at startup. Different codes exist for different errors. This is in place of the normal Happy Mac icon, which indicates that the startup-time hardware tests were successful. The icon itself remained unchanged throughout most of the Classic Mac OS lifespan and was always displayed in black and white; it was never updated to 8-bit color unlike the Happy Mac and its related icons.
Most models made prior to the Macintosh II crash silently and display the Sad Mac without playing any tone. In 68k models made after the Macintosh II, a series of sounds known as the Chimes of Death (see below) are played. Most PowerPC Macs play a sound effect of a car crash, while computers equipped with a PowerPC upgrade card use a three note brass fanfare death chime (A, E-natural, and E-flat) with the sound of drums and cymbals at the end, taken from the Power Macintosh/Performa 6200 and 6300.
A Sad Mac can be deliberately generated at startup by pressing the interrupt switch (Also known as the Programmer's Key) on Macintosh computers that had one installed or by pressing Command and Power keys shortly after the startup chime. These functions normally opened up a debugger window within the operating system but triggers a Sad Mac error on startup when it is accessed before booting into an operating system. On some Macintoshes such as PowerBook 540c, if the user presses the command and power keys before the boot screen is displayed, only the Chimes of Death are played. Depending on the model, the chimes would play much faster or slower than normal and there is no Sad Mac displayed.
Old World ROM Power Macintosh and PowerBook models based on the PCI architecture do not use a Sad Mac icon and will instead only play the error/car-crash sound on a hardware failure (such as missing or bad memory, unusable CPU, or similar errors).
An equivalent to the Sad Mac on macOS is a Universal "no" symbol introduced in Mac OS X 10.2 Jaguar and later, which denotes a hardware or software error that renders the computer non-bootable as well as indicating that an incorrect OS has been found (as mentioned above).[31][32]
Chimes of Death
[edit]The Chimes of Death are the Macintosh equivalent of a beep code on IBM PC compatibles. On all Macintosh models predating the adoption of PCI and Open Firmware, the Chimes of Death are often accompanied by a Sad Mac icon in the middle of the screen (see "Sad Mac" above).
Different Macintosh series have different death chimes. The Macintosh II is the first to use the death chimes, using the Apple Sound Chip to play a loud and eerie upward major arpeggio, with different chimes on many models. The Macintosh Quadra, Centris, Performa, LC, and the Macintosh Classic II play a generally softer and lower pitched version of the upward major arpeggio, followed by three or four notes, with slight variations depending on the model of the Macintosh. The PowerBook 5300, 190, and 1400 use the second half of the 8-note arpeggio as found on the Quadra and Centris models, or the entire death chime if the error occurs before the screen lights up. The Macintosh Quadra/Centris 660AV use a sound of a single pass of the Roland D-50's "Digital Native Dance" sample loop combined with a few sound effects from the Roland U-20, while the NuBus-based Power Macintosh models (including the 6100,[5] 7100, and 8100 series) use a car crash sound made using a assorted collection of sound effects from Elektra Records and Hanna-Barbera.[33][34] The Power Macintosh and Performa 6200 and 6300 series along with the Power Macintosh (PowerPC) upgrade card use an eerily dramatic 3-note brass fanfare with a rhythm of drums and cymbals composed on the Roland U-20. In the case of the Power Macintosh/Performa 6200 and 6300, the aforementioned death chime plays before the screen lights up for these models while the 8-note arpeggio similar to that found in the Quadra and Centris series plays after the screen lights up. The pre-G3 PCI Power Macs, the beige G3 Power Macs, the G3 All-In-One, and the PowerBook 2400, 3400, and G3 all use the sound of popping and glass shattering;[35] these models do not display a Sad Mac icon.
With the introduction of the iMac in 1998, the Chimes of Death are no longer used in favor of a series of tones to indicate hardware errors.[6]
See also
[edit]References
[edit]- ^ "Boot process for an Intel-based Mac". Apple Support. Retrieved September 11, 2024.
- ^ "Boot process for a Mac with Apple Silicon". Apple Support. Retrieved November 6, 2024.
- ^ a b Jarvis, Lon (August 22, 2000). "The Macintosh Boot Sequence". James Madison University. Retrieved November 8, 2024.
- ^ "If your Mac starts up to an Apple logo or progress bar". Apple Support. Retrieved October 11, 2024.
- ^ a b "Weird Mac Startup and Crash Sounds". 512 Pixels. November 14, 2011.
- ^ a b "If your Mac beeps during startup". Apple Support. Retrieved November 9, 2024.
- ^ a b Hardwick, Tim (October 30, 2016). "Classic Mac Startup Chime Not Present in New MacBook Pros". MacRumors. Retrieved October 30, 2016.
- ^ "Turn the Mac startup sound on or off". Apple Support. December 18, 2020.
- ^ Hardwick, Tim (October 30, 2016). "Classic Mac Startup Chime Not Present in New MacBook Pros". MacRumors. Retrieved September 14, 2020.
- ^ a b Hertzfield, Andy (November 19, 2011). Revolution in The Valley [Paperback]: The Insanely Great Story of How the Mac Was Made. O'Reilly Media. ISBN 978-1-4493-1624-2.
- ^ "Mark Lentczner's Curriculum Vitae". October 28, 2005. Archived from the original on October 28, 2005. Retrieved November 7, 2024.
- ^ a b c Whitwell, Tom (May 26, 2005). "Tiny Music Makers: Pt 4: The Mac Startup Sound". Music Thing.
- ^ Broussard, Mitchel (March 24, 2018). "Former Apple Sound Designer Discusses History Behind 'Sosumi', Mac Startup Tone, and Camera Click". Mac Rumors. Retrieved November 13, 2024.
- ^ Pettitt, Jeniece (March 24, 2018). "Meet the man who created Apple's most iconic sounds: Sosumi, the camera click and the start-up chord". CNBC. Retrieved March 24, 2018.
- ^ "The Mystery of the Mac Startup Chime". Constructive Noise vs. WordPress. April 27, 2015. Retrieved October 20, 2024.
- ^ "Current Favorites". December 6, 2000. Archived from the original on December 6, 2000. Retrieved November 8, 2024.
- ^ "Apple's Classic Mac Startup Chime is now a Registered Trademark". Patently Apple. December 12, 2012. Retrieved October 30, 2016.
- ^ "Man Behind the Iconic Apple Mac OS Startup Sound & So-Sue-Me Legend". Obama Pacman. March 10, 2010. Archived from the original on March 13, 2010. Retrieved January 24, 2011.
- ^ Peters, Jay (June 23, 2020). "The Mac's iconic startup chime is back in macOS Big Sur". The Verge. Retrieved June 28, 2020.
- ^ "Pablo Picasso - Two characters, 1934". www.pablo-ruiz-picasso.net. Retrieved December 17, 2023.
- ^ Phin, Christopher (May 11, 2015). "The Finder icon and the influence of fine art on the Mac". Macworld. Retrieved December 17, 2023.
- ^ "TM Research Archive – Interviews". www.tm-research-archive.ch. Retrieved October 26, 2024.
- ^ "Question Mark Disk". Big Mess o' Wires. September 18, 2011. Retrieved November 12, 2024.
- ^ "If your Mac starts up to a circle with a line through it". Apple Support. Retrieved November 12, 2024.
- ^ "OS X Yosemite - Technical Specifications". Apple Support. Retrieved November 11, 2024.
- ^ Strange, Adario (September 14, 2017). "How Apple's iPhone X is using the old 'happy Mac' icon to make Face ID less creepy". Mashable. Retrieved October 4, 2024.
- ^ "Common Mac System Bombs Decoded". Mac GUI. December 6, 2018. Retrieved November 9, 2024.
- ^ "Mac OS X 10.0". Ars Technica. April 2, 2001. Retrieved November 11, 2024.
- ^ "A Brief History Of Kernel Panics". Electric Light Company. July 27, 2024. Retrieved November 10, 2024.
- ^ "Macintosh: "Sad Macintosh" Error Code Meaning". Apple. November 30, 2003. Archived from the original on June 17, 2009. Retrieved August 24, 2008.
- ^ "OS X: "Broken folder" icon, prohibitory sign, or kernel panic when computer starts. Apple". Archived from the original on October 13, 2007. Retrieved July 29, 2010.
- ^ Delio, Michelle (August 2, 2002). "'Happy Mac' Killed By Jaguar". Wired.com. Archived from the original on February 4, 2011.
- ^ "AUTO, SKID". AudioHero.com. Sound Ideas. Retrieved April 27, 2025.
- ^ "Hanna-Barbera Sound Effects Library". SoundIdeas.com. Sound Ideas. Retrieved April 27, 2025.
- ^ "Power Macintosh 9500". MCbx Old Computer Info. February 22, 2018. Retrieved November 10, 2024.
External links
[edit]- The Original Macintosh: Boot Beep – Folklore.org
- Every Mac Startup & Crash Chime on YouTube (2017)
Macintosh startup
View on GrokipediaBoot Process Evolution
Classic Era (1984–1998)
The Classic Era of Macintosh startup, spanning from 1984 to 1998, encompassed the initial boot mechanisms in Apple's computers equipped with Old World ROM firmware, which relied on Motorola 68000-series processors and lacked advanced features like Open Firmware. Introduced with the original Macintosh 128K model on January 24, 1984, this era defined the foundational hardware initialization and operating system loading process for all subsequent 68k-based systems.[9] The boot sequence emphasized reliability through basic self-diagnostics and direct loading from storage media, supporting models up to the Power Mac 4400 and concluding with the beige Power Macintosh G3 series in 1998.[10] Upon powering on, the Power Manager IC—such as the custom 50753 microprocessor in later models—asserts a reset signal to the CPU, halting execution and preparing the system for initialization.[11] The CPU then begins fetching instructions from ROM stored in EPROM chips mapped to address $00000000, executing the initial boot code that clears the video display and generates the startup chime to signal that the initial hardware self-tests have been successfully completed.[11] This ROM-based firmware, typically 64 KB in early models and expanding to 1 MB or more in later ones, handles the core startup logic without external loaders.[12] The ROM firmware performed hardware self-diagnostics—commonly referred to as a Power-On Self-Test (POST)—to validate hardware integrity before proceeding. However, during the Classic Era (1984–1990s), Apple deliberately avoided using the term "POST" and other technical jargon in user-facing elements to maintain a user-friendly, non-technical experience, in contrast to PCs that often relied on explicit beep codes or text messages during startup. Instead, low-level diagnostics were hidden behind intuitive elements: the startup chime indicated successful test completion, the Happy Mac icon appeared upon successful hardware validation, and failures triggered the Sad Mac icon accompanied by error codes or specific chime patterns. This approach aligned with Apple's philosophy of abstracting complexities, utilizing larger ROM sizes to integrate more OS code, and avoiding PC-like terms such as BIOS or POST. Using processors such as the 68000, 68020, 68030, or 68040, these self-tests systematically checked RAM by walking bit patterns through address lines to detect faults or size variations; they also verified NVRAM for parameter storage, VIA chips for I/O interfacing, and the SCSI bus for peripheral connectivity.[13] Failures in these checks triggered error indicators like the "Sad Mac" icon or specific chime patterns, such as slow tones for RAM issues, preventing further boot to avoid instability.[13] Successful completion allowed the ROM to scan boot devices in priority order. If a bootable volume is detected, the ROM loads the System file—a core component of Mac OS—from the floppy disk (in 400 KB or 800 KB MFM format for early models) or hard drive into RAM, decompressing and initializing the Macintosh Toolbox for graphics, events, and resource management.[12] The Finder, serving as the desktop shell, then launches, mounting volumes and rebuilding the desktop database for file icons and aliases.[12] This process, absent in later eras' abstracted firmware, directly tied hardware validation to OS readiness, enabling seamless operation on models from the compact original 128K to tower-based systems like the Power Mac 4400. In later years of this era, some models incorporated PowerPC processors while retaining the 68k emulation layer in ROM for compatibility during the transition.[10]PowerPC Transition (1998–2006)
The PowerPC Transition era marked a significant evolution in Macintosh startup firmware, beginning in August 1998 with the introduction of the iMac G3, the first model to adopt the New World ROM architecture.[14] This shift replaced the limitations of the prior Old World ROM, which restricted booting primarily to internal hard drives and lacked flexible device enumeration. The New World ROM integrated Open Firmware, a standard defined by IEEE 1275, as a Forth-based interpreter embedded in the ROM to provide a machine-independent environment for hardware initialization and OS loading.[15] Open Firmware loaded boot drivers directly from its image in ROM, enabling support for booting from diverse devices such as external drives, networks, or CD-ROMs through plug-and-play probing. Central to the boot process was Open Firmware's device tree probing, which dynamically enumerated hardware components after power-on self-test (POST) diagnostics.[15] It constructed a hierarchical device tree representing the system's topology, identifying elements like the PowerPC G3, G4, or G5 CPU, PCI bus, and peripherals such as USB controllers or Ethernet interfaces.[15] For instance, on iMac G3 systems, Open Firmware configured custom ASICs like UniNorth for memory and I/O bridging, ensuring compatibility with the all-in-one design.[15] This probing phase, executed via Forth scripts, allowed the firmware to adapt to varying hardware configurations without hardcoded assumptions, facilitating the transition from 68k emulation dependencies to native PowerPC execution. Following device tree construction, Open Firmware invoked the graphical bootloader BootX for Mac OS 9 and early Mac OS X systems.[16] BootX, loaded from the blessed System Folder on the boot volume, displayed the iconic Apple logo during initialization and handled kernel loading by injecting necessary drivers for graphics, storage, and input devices.[15] It searched HFS or HFS+ partitions for compatible boot images, such as the "tbxi" files containing the Mac OS ROM image, before transitioning control to the operating system.[15] The full adoption of this architecture occurred with the Power Mac G4 in August 1999, which featured enhanced Open Firmware version 4.1.9 and supported higher-performance G4 processors with AltiVec extensions.[17][15] This era culminated in 2006 with Apple's shift to Intel processors, phasing out PowerPC-specific Open Firmware in favor of EFI-based systems.[18]Intel Era (2006–2020)
The Intel era of Macintosh startup began in January 2006 with the release of the first Intel-based Mac, the iMac, marking Apple's transition from PowerPC processors and Open Firmware to x86 architecture and the Extensible Firmware Interface (EFI). EFI replaced Open Firmware as the firmware standard, providing a standardized interface for booting that facilitated compatibility with x86 hardware and enabled features like faster initialization and support for multiple boot options.[19] This shift allowed Intel-based Macs to boot macOS through a multi-stage process: the EFI firmware initializes hardware and loads the boot.efi loader from the startup disk, which then verifies and loads the kernel (XNU), displaying a progress bar during kernelcache loading to indicate system readiness.[1] The progress bar, visible after the Apple logo, reflects the loading of essential system components and typically completes within seconds on supported hardware.[20] To support dual-booting with Windows on Intel Macs, Apple introduced Boot Camp in 2006, which leverages EFI to partition the drive and install Windows in native EFI mode, providing hardware drivers for seamless operation without virtualization. Boot Camp's EFI implementation ensured that Windows could boot directly via the EFI firmware, selectable through the Startup Manager (accessed by holding the Option key), transitioning from earlier emulation-based approaches to unified firmware handling.[21] This era's boot process emphasized modularity, with EFI allowing updates via macOS software rather than hardware flashes in early models.[22] In 2018, Apple enhanced security in later Intel Macs by integrating the T2 Security Chip, first introduced in the iMac Pro (December 2017) and expanded to models like the 2018 Mac mini, MacBook Pro, and MacBook Air. The T2 chip, a custom ARM-based secure enclave, manages secure boot by verifying the integrity of EFI firmware images and the boot.efi loader using cryptographic signatures before execution, preventing unauthorized modifications.[1] It also integrates Touch ID for user authentication during boot and login, storing biometric data in its Secure Enclave to enable features like firmware password protection and encrypted storage keys.[23] These enhancements rooted the boot chain of trust in hardware, ensuring that only signed macOS components could load. The Intel era concluded in late 2020 with the introduction of the M1 chip in the Mac mini, MacBook Air, and 13-inch MacBook Pro, shifting boot responsibilities to integrated Apple Silicon without discrete T2 chips for firmware handling. Throughout its duration, the EFI-based process provided a stable foundation for macOS versions from 10.4 Tiger to 10.15 Catalina, balancing performance and security on x86 hardware.[19]Apple Silicon Era (2020–present)
The Apple Silicon era of Macintosh startup began on November 10, 2020, with the introduction of the M1 chip in the MacBook Air, MacBook Pro, and Mac mini, marking Apple's shift to its custom ARM-based system-on-chip (SoC) architecture.[24] This integration unifies the CPU, GPU, Neural Processing Unit, Secure Enclave, and other subsystems on a single die with shared unified memory, enabling a streamlined boot process that prioritizes security and efficiency over the modular EFI firmware of prior Intel-based systems.[25] By late 2025, this architecture has advanced to the M5 series chips in models such as the updated MacBook Pro, while persisting in the M4 series across MacBook Air, Mac Studio, and other models, sustaining the era's focus on SoC-driven booting without external BIOS equivalents.[26][27] The boot sequence commences with SecureROM, immutable read-only code embedded in the SoC that establishes the initial chain of trust by cryptographically verifying and loading the Low-Level Bootloader (LLB, or iBoot stage 1) from NOR flash memory.[7] The LLB then authenticates signatures for essential system firmware—such as controllers for storage, display, and the Always-On Processor—while evaluating the LocalPolicy file from the Secure Enclave to enforce security levels like Full Security (latest signed OS only) or Reduced Security (allowing older macOS versions).[7] It provides anti-replay protection via the Secure Storage Component and transitions control to iBoot (stage 2), loaded from NVMe storage.[25] iBoot verifies and loads additional macOS-paired firmware for components like the Secure Neural Engine, authenticates the signed system volume's root hash, and incorporates the Auxiliary Kernel Collection (AuxKC) if permitted by policy before handing off to the macOS kernel, device tree, and trust cache.[7] The kernel then initializes the operating system, with memory protections activated through System Coprocessor Integrity Protection to lock down the runtime environment.[7] Throughout this chain, cryptographic verification using Apple-signed certificates ensures each stage's integrity, blocking unsigned or tampered code; external or third-party booting requires user-approved permissive policies via the Secure Enclave, preventing unauthorized modifications.[25] This secure boot model extends principles from the Intel-era T2 chip's Boot ROM but achieves seamless SoC integration without discrete firmware handoffs.[1] Boot options on Apple Silicon Macs are accessed by holding the power button from a shutdown state, displaying the Startup Options screen for selecting volumes, entering recovery, or configuring settings—no modifier keys are needed, unlike EFI-based systems.[4] To enter macOS Recovery mode, the Mac must be shut down completely, after which the power button is pressed and held until "Loading startup options" appears; users then select Options and click Continue.[8] If prompted for a password, the user may select a startup disk or, in cases of forgotten credentials, enter the known admin password and select “Forgot all passwords?” to proceed with recovery.[28] Recovery modes include the paired recoveryOS, loaded via the standard LLB-iBoot path for diagnostics and reinstallation, accessible by holding the power button until options appear.[29] If the paired version fails, fallback recoveryOS activates via double-pressing and holding the power button, providing a verified alternate kernel collection from sealed storage as a fail-safe without BIOS-level intervention.[29] Safe Mode, for troubleshooting, boots macOS sans AuxKC after selecting from recoveryOS while holding Shift.[29]Audio Cues
Startup Chime History
The startup chime of the Macintosh, a distinctive audio cue played upon successful completion of the Power-On Self-Test (POST), originated with the original Macintosh 128K in 1984 as a simple square-wave beep generated at a gradually incrementing frequency via the onboard MOS 6522 Versatile Interface Adapter (VIA) chip, programmed by software engineer Andy Hertzfeld and refined by Charlie Kellner.[30] This early sound served as a basic indicator of hardware functionality but was considered rudimentary and lacking in character.[30] In 1991, with the introduction of the Macintosh Quadra 700, Apple sound designer Jim Reekes replaced the beep with a more sophisticated stereo C major chord, recorded using a Korg Wavestation synthesizer to evoke a sense of calm and reliability; the chord featured string-like tones with a "chiffy" bamboo attack, reverb, and a left-to-right panning fade for spatial depth.[2][31] This design prioritized compatibility across diverse audio outputs, from basic built-in speakers to professional setups, and became a hallmark of Apple's branding.[2] The chime evolved further in 1998 with the iMac G3, shifting to an F-sharp major chord derived by pitch-shifting the prior version, which remained standard through the PowerPC and early Intel eras until minor adjustments for audio hardware improvements.[32] In 2012, Apple secured a U.S. registered trademark for this sound (Serial No. 85663397), recognizing its role as a proprietary auditory identifier.[33] Starting with the 2016 MacBook Pro models and macOS Sierra, Apple disabled the chime by default to support silent booting in quiet environments, such as when opening the lid on portable Macs, though it could be re-enabled via Terminal commands likesudo nvram StartupMute=%00.[34] The sound returned as a default feature in macOS Big Sur (2020), now an F major chord—a semitone lower than the previous iteration for a warmer tone—and made toggleable via System Preferences > Sound > Sound Effects > "Play sound on startup."[35][36]
Technically, early iterations like the 1984 beep were software-generated using assembly code on the Motorola 68000 processor, while Reekes' versions from the Quadra era onward utilized sampled audio played through the system's digital-to-analog converter, transitioning to firmware-integrated playback in later PowerPC and Intel models before becoming software-controlled again in the Apple Silicon transition.[30][2]
Error Chimes
The error chimes, commonly referred to as the Chimes of Death, were distinctive audio signals emitted by Macintosh computers to indicate severe hardware failures or boot errors during the power-on self-test. Introduced with the Macintosh II in 1987, these chimes alerted users to issues such as ROM corruption or RAM faults on 68k-based systems, playing immediately upon detection to accompany the Sad Mac icon.[37] Specific to models from the classic era (1987–1998), the Chimes of Death featured tonal patterns that varied by hardware, often involving a series of descending and ascending notes generated through the system's sound hardware during ROM diagnostics. For instance, the Macintosh II and its variants like the IIcx produced a characteristic error tone sequence signaling vertical sync or memory test failures.[37] These chimes functioned purely as hardware-initiated diagnostics, providing no software-based workaround or equivalent, and required physical intervention to resolve underlying problems like defective ROM chips or incompatible RAM configurations. Their role emphasized early Macintosh design principles, where auditory feedback complemented limited visual diagnostics on monochrome displays.[37] In the PowerPC transition period (1994–2006), error chimes appeared less frequently, with select models such as the Power Mac 6100 employing a harsher "car crash" variant for boot failures, though usage diminished as ROM designs evolved.[37] By the Intel era (2006–2020) and into the Apple Silicon era (2020–present), the Chimes of Death were entirely supplanted by visual failure indicators and standardized beep patterns, such as a single long tone for no RAM detection or four short beeps for faulty memory slots, reflecting a shift toward more precise, silent error reporting.[38]Visual Indicators
Success Symbols
The Happy Mac, a bitmap icon depicting a smiling computer face, was the initial visual symbol of successful Macintosh startup from 1984 to 2002. Created by graphic designer Susan Kare for the original Macintosh, this 42-pixel image was embedded in the system's ROM and appeared immediately after the Power-On Self-Test (POST) confirmed hardware integrity, reassuring users of a functional boot sequence.[39][40][41] Beginning with Mac OS X 10.2 Jaguar in 2002, Apple replaced the Happy Mac with a gray Apple logo centered on a uniform gray background, accompanied by a spinning gear beneath it to denote ongoing system loading. This minimalist design persisted through subsequent releases, evolving to a full-color Apple logo by Mac OS X 10.5 Leopard in 2007, enhancing visual clarity during the boot phase.[42][43][44] In OS X 10.9 Mavericks released in 2013, Apple introduced a progress bar below the logo, filling gradually to provide tangible feedback on boot advancement and kernel loading. Since macOS 10.14 Mojave in 2018, the interface incorporates dark mode variants, inverting colors to a black background with a white logo for systems set to dark appearance. These symbols are generated by the bootloader—BootX for classic Mac OS or boot.efi for macOS—signaling the successful handoff from firmware initialization to the operating system kernel.[44][45] The visuals typically coincide with the startup chime for auditory confirmation.[46]Failure Symbols
The Sad Mac icon, featuring a frowning face on a black screen, indicated severe hardware failures during the boot process of Macintosh computers from their introduction in 1984 through the classic era until approximately 1998. Accompanied by the Chimes of Death audio tones, it signaled issues detected during power-on self-tests, such as faulty CPU, memory, or ROM components.[47] These failures were detailed by two lines of four-digit hexadecimal error codes in the format XXXXYYYY over ZZZZZZZZ, where the upper line represented the phase of failure and the lower line provided diagnostic specifics. Technicians used these codes to isolate problems like defective chips or addressing line failures.[47][48] A second key failure symbol, the flashing question mark inside a folder icon, appears when the Mac cannot locate a valid startup disk, a condition present since the 1984 Macintosh 128K. This visual cue, often on a white or gray background, originally instructed users to insert a floppy disk containing the System software. In later classic models supporting network booting, the flashing folder evolved into a spinning globe during network-based OS loading attempts.[49] The flashing question mark folder persists in Mac OS X and modern macOS to indicate no bootable operating system, specifically that the Mac cannot locate a valid startup disk or a working macOS installation, distinct from the prohibitory circle-slash symbol used for hardware or firmware incompatibilities.[49][50][51] If the icon appears persistently, users can troubleshoot by first attempting to access the Startup Manager to select a boot disk: on Intel-based Macs, restart and hold the Option key during startup; on Apple silicon Macs, press and hold the power button until "Loading startup options" appears, then select the desired disk. If this fails, boot into macOS Recovery: on Intel-based Macs, restart and immediately hold Command (⌘)-R until the Apple logo or spinning globe appears; on Apple silicon Macs, press and hold the power button until "Loading startup options" appears, then select Options and Continue. In Recovery mode, open Disk Utility to repair the startup disk using First Aid. If repair fails or the disk is missing, erase the disk (if needed) and reinstall macOS. If the disk does not appear in Disk Utility or erasing fails, check connections and cables for external drives, shut down and unplug nonessential devices, then retry, or seek Apple service for potential hardware issues.[49][8] If the question mark appears briefly before normal boot, check the Startup Disk settings in System Settings. If the issue persists, reset NVRAM on Intel Macs: shut down the Mac, turn it on, and immediately hold Option-Command-P-R for 20 seconds until the Mac appears to restart (this does not apply to Apple silicon Macs).[49][52] As of 2025 (with the relevant Apple support article last updated December 2025) and into 2026, there have been no major changes to this issue or its fixes, which remain standard per Apple's support documentation.[49] The Sad Mac was discontinued around the late 1990s with the transition to New World ROMs on later PowerPC models, while the flashing question mark folder persisted in Mac OS X and modern macOS to indicate no bootable operating system, distinct from the prohibitory circle-slash symbol used for hardware or firmware incompatibilities.[50][51]Error States
Hardware Diagnostics
In the early Macintosh era, prior to 1998, hardware diagnostics during startup primarily relied on the "Sad Mac" icon, which displayed alongside hexadecimal error codes to indicate specific hardware failures detected during the Power-On Self-Test (POST). For example, a code such as 0000000F 00000002 often signaled a RAM test failure, pointing to issues like faulty memory modules or logic board problems. These codes were generated by the Macintosh's ROM-based diagnostics, which tested critical components like the CPU, memory, and bus integrity before loading the operating system; if a failure occurred, the system halted with the Sad Mac face and code, often accompanied by an error chime. Apple technicians used detailed code tables to troubleshoot, as outlined in official service documentation from the period. During the Intel transition starting in 2006, Apple introduced the Apple Hardware Test (AHT), a dedicated diagnostic utility provided on CD-ROM or the original installation DVDs for models up to early 2013. Users accessed AHT by restarting the Mac and holding the D key, which booted into a menu-driven interface testing components such as the logic board, memory, hard drive, and video systems; extended tests could run for hours to identify intermittent faults. For Macs without the original media, internet-based AHT downloads were available via Option-D at startup, allowing remote retrieval over Wi-Fi. AHT reported issues with reference codes like ADP000 for no problems or specific identifiers for failures, such as memory errors (e.g., 4HDD/11/40000000: Smart self-test failed). This tool was essential for diagnosing startup failures caused by hardware degradation, like bad sectors on the hard drive that prevented OS loading, which could be verified and repaired using Disk Utility in recovery mode. From mid-2013 onward, Apple Diagnostics replaced AHT as the standard hardware testing application, integrated into the firmware for Intel-based Macs and accessible by holding the D key (or Option-D for internet mode) during startup. This utility performs automated checks on the logic board, memory, storage, Wi-Fi, and other peripherals, displaying results with reference codes (e.g., ADP000 for no issues or PPP001 for power supply problems) and recommending actions like contacting Apple Support. For Macs with the T2 security chip (introduced in 2018), diagnostics include built-in security verifications through the Startup Security Utility, accessible in macOS Recovery mode via Utilities > Startup Security Utility, which configures secure boot policies and external media allowances while running integrity checks on firmware and storage encryption.[53][23] In the Apple Silicon era (2020–present), hardware diagnostics maintain continuity with prior systems but adapt to the integrated SoC architecture, started by pressing and holding the power button until “Loading startup options” appears, then releasing the power button and immediately pressing and holding the Command (⌘)-D keys. This launches Apple Diagnostics, which tests the unified memory, SSD controller, sensors, and display pipelines, often completing in under five minutes and providing codes like ADP000 for no issues found or storage-specific alerts for bad sectors that could halt boot by corrupting the system volume. Common hardware-related startup issues across eras include faulty PRAM/NVRAM, which stores boot settings and can cause failure to recognize the startup disk if corrupted—resolved by resetting via Command-Option-P-R at startup on Intel Macs or through Terminal in recovery on Apple Silicon—and bad sectors on the drive, detectable via First Aid in Disk Utility to repair or isolate faulty areas before reinstalling macOS.[53][4][54]Software Panics
In Classic Mac OS, software panics were indicated by the "bomb screen," an alert featuring an exploding bomb icon designed by Susan Kare to signify a fatal system error. This icon appeared from the original Macintosh in 1984 until the transition to Mac OS X in 2001, typically triggered by low-level issues such as bus errors (attempts to access invalid memory addresses) or address errors (misaligned data access), often resulting from memory corruption or hardware-software mismatches during application execution or system initialization. Stack overflows, where recursive calls or excessive data pushed the stack beyond limits, could also provoke these panics by causing arithmetic overflows or privilege violations, leading to an immediate halt and the bomb dialog with an error code for user reference. Unlike hardware failures like the Sad Mac, which occurred pre-OS, these were OS-level crashes resolvable by restarting or using extensions managers to disable faulty INITs. With the introduction of Mac OS X in 2001, the bomb screen was replaced by the kernel panic, a protective mechanism where the XNU kernel detects irrecoverable errors and halts the system to prevent further damage. Early versions (OS X 10.0 to 10.7, 2001–2011) displayed a gray screen overlaid with multilingual text instructing a restart, accompanied by verbose debug information including stack traces and register dumps to aid developers. From OS X 10.8 Mountain Lion (2012) onward, the screen shifted to black (informally called "Picasso" due to its abstract text rendering) until macOS Mojave (2018), retaining debug details but simplifying the visual for better readability on Retina displays. Causes commonly included driver conflicts (e.g., incompatible kernel extensions or third-party graphics drivers) and memory corruption during extension loading at boot, where faulty kexts failed to initialize properly. Recovery from kernel panics emphasized isolating software issues: For Intel-based Macs, booting into Safe Mode by holding the Shift key during startup loads only essential drivers and extensions, allowing users to uninstall problematic software or run diagnostics. For Apple silicon Macs, shut down the Mac, press and hold the power button until startup options appear, select the startup volume, press and hold the Shift key, then click Continue in Safe Mode. For deeper troubleshooting, verbose mode—activated by setting the boot-args NVRAM variable to "-v" (e.g., vianvram boot-args="-v" in Terminal)—displays real-time boot logs, revealing the exact point of failure such as a corrupted module load. Apple recommends disconnecting peripherals and updating software as initial steps, with panic logs stored in /Library/Logs/DiagnosticReports for analysis.
The evolution continued into the Apple Silicon era (2020–present), where kernel panics no longer show a persistent screen; instead, the display flashes purple and the system reboots immediately, omitting debug text to prioritize rapid recovery and security on M-series chips. This design reduces user exposure to sensitive kernel data while logs remain accessible post-reboot, reflecting Apple's shift toward more resilient architecture without the visual drama of earlier panics.
Booting from External Media
A common startup failure involves bootable external media, such as USB installers for macOS recovery or installation, not appearing in the boot volume selection interface—Startup Manager on Intel-based Macs or the startup options screen on Apple Silicon Macs—preventing selection for booting. On Intel-based Macs, holding the Option (⌥) key during startup accesses Startup Manager, which lists available boot volumes including external drives. Failure to display a bootable USB often results from improper preparation of the media. The drive must be created using Apple'screateinstallmedia command in Terminal, which erases and formats the USB correctly. Manual formatting must use GUID Partition Map scheme and Mac OS Extended (Journaled) file system. Other causes include faulty USB drive, port, or cable; unrecognized hardware; or, on models with the Apple T2 Security Chip (2018–2020), Startup Security Utility (accessed in macOS Recovery) not configured to allow booting from external or removable media. Bootable installers do not appear in System Settings > Startup Disk, which lists only permanent startup disks, not one-time boot options. Resetting NVRAM (Command-Option-P-R at startup) may resolve recognition issues.[55][4][56][57]
On Apple Silicon Macs, holding the power button until the startup options screen appears displays available volumes. Similar preparation issues prevent a bootable USB from appearing, primarily improper creation or formatting (official process uses Mac OS Extended Journaled via createinstallmedia). Unlike T2-equipped Intel Macs, Apple Silicon does not require Startup Security Utility (replaced by Startup Disk security policy controls) to enable external booting; it is supported when the media is correctly prepared. Troubleshooting mirrors Intel methods: recreate the installer per Apple's guide, verify formatting with Disk Utility, and test alternative ports, drives, or cables.[55][4][57][58]