Mac OS
By Wikipedia,
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http://en.wikipedia.org/wiki/Mac_OS
http://en.wikipedia.org/wiki/Mac_OS_history
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Mac
OS is the trademarked name for a series of graphical
user interface-based operating systems developed by Apple
Inc. (formerly Apple Computer, Inc.) for their Macintosh
line of computer systems. The Macintosh user experience
is credited with popularizing the graphical user interface.
The original form of what Apple would later name the "Mac
OS" was the integral and unnamed system software first
introduced in 1984 and later in 1997 with the original Macintosh,
usually referred to simply as the System software.
Apple deliberately downplayed the existence of the operating
system in the early years of the Macintosh to help make
the machine appear more user-friendly and to distance it
from other operating systems such as MS-DOS, which were
portrayed as arcane and technically challenging. Much of
this early system software was held in ROM, with updates
typically provided free of charge by Apple dealers on floppy
disk. As increasing disk storage capacity and performance
gradually eliminated the need for fixing much of an advanced
GUI operating system in ROM, Apple explored cloning while
positioning major operating system upgrades as separate
revenue-generating products, first with System 7 and System
7.5, then with Mac OS 7.6 in 1997.
Earlier versions of the Mac OS were compatible only with
Motorola 68000-based Macintoshes. As Apple introduced computers
with PowerPC hardware, the OS was upgraded to support this
architecture as well. Mac OS X, which has superseded the
"Classic" Mac OS, is compatible with both PowerPC
and Intel processors.
Versions
The early Macintosh operating system initially consisted
of two pieces of software, called "System" and
"Finder", each with its own version number.
System 7.5.1 was the first to include the Mac OS logo (a
variation on the original "Happy Mac" smiley face
Finder startup icon), and Mac OS 7.6 was the first to be
named "Mac OS" (to ensure that users would still
identify it with Apple, even when used in "clones"
from other companies.
Until the advent of the later PowerPC G3-based systems,
significant parts of the system were stored in physical
ROM on the motherboard. The initial purpose of this was
to avoid using up the limited storage of floppy disks on
system support, given that the early Macs had no hard disk.
(Only one model of Mac was ever actually bootable using
the ROM alone, the 1991 Mac Classic model.) This architecture
also allowed for a completely graphical OS interface at
the lowest level without the need for a text-only console
or command-line mode. A fatal software error, or even a
low-level hardware error discovered during system startup
(such as finding no functioning disk drives), was communicated
to the user graphically using some combination of icons,
alert box windows, buttons, a mouse pointer, and the distinctive
Chicago bitmap font. Mac OS depended on this core system
software in ROM on the motherboard, a fact that later helped
to ensure that only Apple computers or licensed clones (with
the copyright-protected ROMs from Apple) could run Mac OS.
The Mac OS can be divided into two families of
operating systems:
- "Classic" Mac OS, the system which shipped
with the first Macintosh in 1984 and its descendants,
culminating with Mac OS 9.
- The newer Mac OS X (where the X is 10 written as a Roman
numeral). Mac OS X incorporates elements of OpenStep (thus
also BSD Unix and Mach) and Mac OS 9. Its low-level BSD-based
foundation, Darwin, is free software/open source software.
History of Mac OS
On January 24, 1984, Apple Computer, Inc. (now Apple Inc.)
introduced the Apple Macintosh personal computer, with the
Macintosh 128K model, which came bundled with the Mac OS
operating system, then known as the System Software. The Macintosh is often credited with popularizing
the graphical user interface. The Mac OS has been pre-installed
on almost every Macintosh computer ever sold. The operating
system is also sold separately at Apple retail stores, and
online. The original Mac OS was partially based on the Lisa
OS, previously released by Apple for the Lisa computer in
1983 and, as part of an agreement allowing Xerox to buy
shares in Apple at a favourable rate, it also used concepts
from the Xerox PARC Xerox Alto which Steve Jobs and several
other Macintosh team members had previewed.
Early history
Development
The Macintosh project started in early 1979 with Jef Raskin,
who envisioned an easy-to-use, low-cost computer for the
average consumer. In September 1979, Raskin was given permission
to start hiring for the project and was, in particular,
looking for an engineer that could put together a prototype.
Bill Atkinson, a member of the Apple Lisa team, introduced
him to Burrell Smith, a service technician who had been
hired earlier that year.
In January 1981, Steve Jobs completely took over the Macintosh
project. Jobs and a number of Apple engineers visited Xerox
PARC in December 1979, three months after the Lisa and Macintosh
projects had begun. After hearing about the pioneering GUI
technology being developed at Xerox PARC from former Xerox
employees like Raskin, Jobs negotiated a visit to see the
Xerox Alto computer and Smalltalk development tools in exchange
for Apple stock options. The final Lisa and Macintosh operating
systems mostly used concepts from the Xerox Alto, but many
elements of the graphical user interface were created by
Apple including the menubar and pop-up menus. The click-and-drag
concept was developed by Jef Raskin.
Unlike the IBM PC, which used 8 kB of system ROM for power-on
self-test (POST) and basic input/output chores (BIOS), the
Mac ROM was significantly larger (64 kB) and held key OS
code. Much of the original Mac ROM was coded by Andy Hertzfeld,
a member of the original Macintosh team. He was able to
conserve some of the precious ROM space by interleaving
some of the assembly language code. In addition to coding
the ROM, he also coded the kernel, the Macintosh Toolbox
and some of the desktop accessories (DAs) as well. The icons
of the operating system, which represented folders and application
software were designed by Susan Kare, who later designed
the icons for Microsoft Windows 3.0. Bruce Horn and Steve
Capps wrote the Macintosh Finder as well as a number of
Macintosh system utilities.
Apple was very strong in advertising their newfound machine.
After it was created, the company bought all 39 pages of
advertisement space in the Newsweek magazine, 1984 November/December
edition. Apple was so successful in its marketing for the
Macintosh, that it quickly outshone its more sophisticated
predecessor, the Lisa, in sales – so much so that Apple
quickly developed a product called MacWorks which allowed
the Lisa to emulate Macintosh system software through System
3, by which time it had been discontinued as the re-branded
Macintosh XL. Many of Lisa's operating system advances would
not appear in the Macintosh OS until System 7.
Release
The first version of the Mac OS (simply called System)
is easily distinguished between other operating systems
from the same period because it does not use a command line
interface; it was one of the first operating systems to
use an entirely graphical user interface. Additional to
the system kernel is the Finder, an application used for
file management, which also displays the Desktop. The two
files were contained in a folder directory labeled System
Folder, which contained other resource files, like a printer
driver, needed to interact with the System.
System 1, 2, 3 & 4
These releases could only run one application at a time,
though special application shells such as Switcher (discussed
under MultiFinder) could work around this to some extent.
System 1.0, 1.1, and 2.0 used a flat file system with only
one kludged level of folders, called Macintosh File System
(MFS); its support for folders (subdirectories) was incomplete.
System 2.0 added support for AppleTalk and the newly introduced
LaserWriter to use it. System 2.1 (Finder 5.0) introduced
the HFS (Hierarchical File System) which had real directories.
This version was specifically to support the Hard Disk 20
and only implemented HFS in RAM, startup and most floppy
disks remained MFS 400K volumes. System 3.0 was introduced
with the Mac Plus, officially implementing HFS and 800K
startup drives and adding support for several new technologies
including SCSI and AppleShare and introducing Trash "bulging"
(i.e., when the Trash contained files, it would gain a bulged
appearance). System 4.0 came with the Mac SE and Macintosh
II, which required additional support for the first expansion
slots, the Apple Desktop Bus (ADB), internal hard drives
and on the Mac II, color, larger displays and the first
Motorola 68020 processor.
Changes in early Macintosh operating systems are best reflected
in the version number of the Finder, where major leaps are
found between 1.x, 4.x, 5.x, and 6.x.

Original 1984 Mac OS desktop
|
System Software
Release |
System Version |
Release Date |
Finder Version |
LaserWriter
Version |
Release Information |
| Mac System Software |
1.0 (.97) |
January 24, 1984 |
1.0 |
|
Initial Release |
| Mac System Software (0.1) |
1.1 |
May 5, 1984 |
1.1g |
|
Maintenance Release, Added Mountain scene, About box,
Clean Up Command |
| Mac System Software (0.3 & 0.5) |
2.0 |
April 1985 |
4.1 |
|
Finder Update |
| System software |
2.1 |
September 1985 |
5.0 |
|
Release for Hard Disk 20 support |
| Mac System Software (0.7) |
3.0 |
January 1986 |
5.1 |
1.1 |
Introduced with Mac Plus |
| System Software 1.0 |
3.1 |
February 1986 |
5.2 |
1.1 |
|
| System Software 1.1 |
3.2 |
February 1986 |
5.3 |
3.1 |
Fixed problems with data loss, system crashes; updated
Chooser and Calculator |
| System Software 2.0 |
3.3 |
January 1987 |
5.4 |
3.1 |
Release for Macintosh II and SE |
| System software |
3.4 |
|
6.1 |
|
Release for Macintosh 512Ke AppleShare 2.0 support |
| System Software 2.01 |
4.0 |
March 1987 |
5.4 |
3.3 |
Introduced AppleShare |
| System Software 2.01 |
4.1 |
April 1987 |
5.5 |
4.0 |
Maintenance Release of System Software. Updated LaserWriter
Driver |
System Software 5
System Software 5 (also referred to as simply System 5)
added MultiFinder, an extension which let the system run
several programs at once. The system used a co-operative
multitasking model, meaning that time was given to the background
applications only when the running application yielded control.
A clever change in system functions that applications were
already calling to handle events made many existing applications
share time automatically. Users could also choose to not
use MultiFinder, and thus stick with using a single application
at a time as in previous releases of the system software.
System Software 5 was also the first Macintosh operating
system to be given a unified "Macintosh System Software"
version number, as opposed to the numbers used for the System
and Finder files.
System Software 5 was available for a very short time and
only in some countries, including the United States.
| System Software
Release |
System Version |
Release Date |
Finder Version |
Multi Finder
Version |
Laser Writer
Version |
Release Information |
| 5.0 |
4.2 |
1987 circa |
6.0 |
1.0 |
5.0 |
Initial Release |
| 5.1 |
4.3 |
1988 circa |
6.0 |
1.0 |
5.1 |
Updated LaserWriter Driver and new version of Apple
HD SC Setup |
System Software 6
System Software 6 (also referred to as simply System 6)
was a consolidation release of the Mac OS, producing a complete,
stable, and long-lasting operating system. Two major hardware
introductions requiring additional support under System
6 were the 68030 processor and 1.44MB SuperDrive debuting
with the Macintosh IIx and Macintosh SE/30. Later it would
include support for the first specialized laptop features
with the introduction of the Macintosh Portable. From System
6 forward, the Finder would have a unified version number
closely matching that of the System, alleviating much of
the confusion caused by the often considerable differences
between earlier Systems.
| System Version |
Release Date |
Finder Version |
Multi Finder
Version |
Laser Writer
Version |
Release Information |
| 6.0 |
April, 1988 |
6.1 |
6.0 |
5.2 |
Initial Release |
| 6.0.1 |
September 19,
1988 |
6.1.1 |
6.0.1 |
5.2 |
Release for Macintosh IIx (1988) |
| 6.0.2 |
Late 1988 |
6.1 |
6.0.1 |
5.2 |
Maintenance Release |
| 6.0.3 |
March 7, 1989 |
6.1 |
6.0.3 |
5.2 |
Release for Macintosh IIcx (1989) |
| 6.0.4 |
September 20, 1989 |
6.1.4 |
6.0.4 |
5.2 |
Release for Macintosh IIfx (1990) |
| 6.0.5 |
March 19, 1990 |
6.1.5 |
6.0.5 |
5.2 |
Not released because of AppleTalk bug |
| 6.0.6 |
October 15, 1990 |
6.1.6 |
6.0.6 |
5.2 |
Initial Release |
| 6.0.7 |
October 16, 1990 |
6.1.7 |
6.0.7 |
5.2 |
Official release for Macintosh LC, IIsi and Classic
(1990) |
| 6.0.8 |
April, 1991 |
6.1.8 |
6.0.8 |
7.0 |
Updated printing software to match software of System
7.0 |
| 6.0.8L |
Late 1991/Early 1992 |
6.1.8 |
6.0.8 |
7.0 |
Limited maintenance release for Pacific customers |
System 7
On May 13, 1991 System 7 was released. It was the second
major upgrade to the Mac OS, adding a significant user interface
overhaul, new applications, stability improvements and many
new features. Its introduction coincided with the release
of and provided support for the 68040 Macintosh line.

Screenshot of System 7.5.3 Revision 2
Perhaps the most significant feature of System 7 was page
swapping support, which previously had only been available
as a third-party add-on. Accompanying this was a move to
32-bit memory addressing, necessary for the ever-increasing
amounts of RAM available to the Motorola 68030 CPU. Earlier
versions of Mac OS had used the lower 24 bits for addressing,
and the upper 8 bits for flags. This had been an effective
solution for earlier Macintosh models with very limited
amounts of RAM, but it became a liability later. Apple described
code that assumed the 24 + 8-bit addressing as being "not
32-bit clean", and most such applications would crash
when 32-bit addressing was enabled by the user. The original
Macs used the Motorola 68000 CPU which could address only
16 MB of memory. 24 Bits is all that is needed to address
the 16MB memory space. This was a hardware limitation, not
a system software design fault. The 68020/68030/68040 CPUs
have 32-bit address buses and can address up to 4 GB of
physical memory. As Apple moved to the 68030 CPU it needed
to allow the use of more than 16 MB of memory. Thus the
transition to 32-bit clean ROMs and software had to be implemented.
One notable System 7 feature was the built-in co-operative
multitasking. In System Software 6, this function was optional
through the MultiFinder. System 7 also introduced aliases,
similar to shortcuts that were introduced in later versions
of Microsoft Windows. System extensions were enhanced, by
being moved to their own subfolder; a subfolder in the System
Folder was also created for the control panels. In System
7.5, Apple included the Extensions Manager, a previously
third-party program which simplified the process of enabling
and disabling extensions.
The Apple menu, home only to desk accessories in System
6, was made more general-purpose: the user could now make
often-used folders and applications—or anything else they
desired—appear in the menu by placing aliases to them in
an "Apple Menu Items" subfolder of the System
Folder. AppleScript, a scripting language for automating
tasks, was also introduced with System 7. 32-bit QuickDraw,
supporting so-called "true color" imaging, was
also included as standard; it was previously available as
a system extension. TrueType, an outline font standard,
was also introduced with System 7.
The Trash, under System 6 and earlier, would empty itself
automatically when shutting down the computer or, if MultiFinder
were not running, when launching an application. System
7 reimplemented the Trash as a special hidden folder, allowing
files to remain in it across reboots until the user deliberately
chose the "Empty Trash" command.
System 7.1 was mainly a bugfix release, with a few minor
features added. System 7.1 was not only the first operating
system to cost money (all previous versions were free or
sold at the cost of the floppies), but also received a "Pro"
sibling with extra features. System 7.1.2 was the first
version to support PowerPC-based Macs. System 7.1 also introduced
the System Enablers as a method to support new models without
updating the actual System file. This led to extra files
inside the system folder (one per new model supported) that
some users found unpleasing.
System 7.5 introduced a large number of "high level"
additions, considered by some to be less well thought-out
than they could have been. Many of the
new features were based on shareware applications that Apple
bought and included into the new system. On the newer PowerPC
machines, System 7.5 was plagued by stability problems due
partly to a new memory manager (which can be turned off),
and poor OS handling of errors in PowerPC code (all PowerPC
exceptions map to Type 11). These growing pains did not
afflict the 68k-architecture machines.
Mac OS 7.6
Stability improved in PPC Macs with Mac OS 7.6, which dropped
the "System" moniker as a more-trademarkable name
was needed in order to license the OS to the growing market
of third-party Macintosh clone manufacturers. Mac OS 7.6
required a 68030 CPU and 32 bit clean ROMs, and so dropped
support for many of the early Macs, including the Mac Plus
and Mac II. Mac OS 7.6.1 finally introduced proper error
handling for PowerPC code, so that errors in PowerPC code
did not always force an immediate reboot.

Mac OS 7.6.1 performing various tasks
Although the version number was subsequently changed to
8.x and 9.x, the internal core of the OS (except the nanokernel,
which was replaced by a new one that support Multiprocessing
Services 2.x in Mac OS 8.6) remained basically the same.
Version history
- System 7.0 (released in late 1991; integrated MultiFinder
always enabled)
- System 7.0.1 (introduced with LC II and Quadra series)
- System 7 Tuner (update for both 7.0 and 7.0.1)
- System 7.1
- System 7.1 Pro (version 7.1.1, combined with PowerTalk,
Speech Manager & Macintalk, Thread Manager)
- System 7.1.2 (first version for Macs equipped with a PowerPC
processor)
- System 7.1.2P (only for Performa/LC/Quadra 630 series,
very quickly replaced by 7.5)
- System 7.5
- System 7.5.1 (System 7.5 Update 1.0 — the first Macintosh
operating system to call itself "Mac OS")
- System 7.5.2 (first version for Power Macs that use PCI
expansion cards, usable only on these Power Macs and PowerBooks
5300 and Duo 2300)
- System 7.5.3 (System 7.5 Update 2.0)
- System 7.5.3L (only for Mac clones)
- System 7.5.3 Revision 2
- System 7.5.3 Revision 2.1 (only for Performa 6400/180
and 6400/200)
- System 7.5.4, released very briefly and withdrawn within
hours. Replaced by 7.5.5
- System 7.5.5 Last to support non-32 bit clean Macs, including
all with less than a 68030 CPU.
- Mac OS 7.6 (name formally changed because of the experimental
clone program, although System 7.5.1 and later used the
"Mac OS" name on the splash screen)
- Mac OS 7.6.1 Proper PowerPC error handling introduced.
Performas used to have their own, exclusive operating
system before they were merged into System 7.5.
- System 7.0.1P
- System 7.1P
- System 7.1P1
- System 7.1P2
- System 7.1P3 (last release with new features)
- System 7.1P4
- System 7.1P5
- System 7.1P6
Mac OS 8
Mac OS 8 was released on July 26, 1997, shortly after Steve
Jobs returned to the company. It was mainly released to
keep the Mac OS moving forward during a difficult time for
Apple. Initially planned as Mac OS 7.7, it was renumbered
"8" to exploit a legal loophole to accomplish
Jobs's goal of terminating third-party manufacturers' licenses
to System 7 and shutting down the Macintosh clone market.
8.0 added a number of features from the stillborn Copland
project, while leaving the underlying operating system unchanged.
A multi-threaded Finder was included, enabling better multi-tasking.
The GUI was changed in appearance to a new shaded greyscale
look called Platinum, and the ability to change the appearance
themes (also known as skins) was added with a new control
panel. This capability was provided by a new "appearance"
API layer within the OS, one of the few significant changes.

Mac OS 8.1 desktop
Apple sold 1.2 million copies of Mac OS 8 in its first
two weeks of availability and 3 million within six months.
In light of Apple's financial difficulties at the time,
there was a large grassroots movement among Mac users to
upgrade and 'help save Apple'. Even some pirate groups refused
to redistribute the OS.
Mac OS 8.1 saw the introduction of an updated version of
the Hierarchical File System called HFS Plus, which fixed
many of the limitations of the earlier system (HFS Plus
continues to be used in Mac OS X). There were some other
interface changes such as separating network features from
printing (the venerable, and rather odd Chooser was at last
headed for retirement), and some improvements to application
switching. However, in underlying technical respects, Mac
OS 8 was not very different from System 7.
Mac OS 8.5 focused on speed and stability, with lots of
old 68k code replaced by modern code native to the PowerPC.
It also improved the appearance on the system, although
the theming feature was cut late in development.
- Mac OS 8.0 (first version to require a 68040 processor,
dropping support for the remainder of the Macintosh II series
and other 68030 Macs)
- Mac OS 8.1 (last version to run on a 68K processor, added
support for USB on the Bondi iMac, added support for HFS+)
- Mac OS 8.5 (first version to run only on a PowerPC processor,
added built-in support for Firewire on the PowerMac G3)
- Mac OS 8.5.1
- Mac OS 8.6 (included a new nanokernel for improved performance
and Multiprocessing Services 2.0 support, added support
for the PowerPC G4 processor)
Mac OS 9
Mac OS 9 was released on October 23, 1999. It was generally
a steady evolution from Mac OS 8. Early development releases
of Mac OS 9 were numbered 8.7. Mac OS 9 added improved support
for AirPort wireless networking. It introduced an early
implementation of multi-user support (though not considered
a true multi-user operating system by modern standards).
An improved Sherlock search engine added several new search
plug-ins. Mac OS 9 also provided a much improved memory
implementation and management. AppleScript was improved
to allow TCP/IP and networking control. Mac OS 9 also made
the first use of the centralized Apple Software Update to
find and install OS and hardware updates. Other new features
included its on-the-fly file encryption software with code
signing and Keychain technologies, Remote Networking and
File Server packages and much improved list of USB drivers.
Mac OS 9 also added some transitional technologies to help
application developers adopt some Mac OS X features before
the introduction of the new OS to the public, again easing
the transition. These included new APIs for the file system,
and the bundling of the Carbon library that apps could link
against instead of the traditional API libraries — apps
that were adapted to do this can be run natively on Mac
OS X as well. Other changes were made in Mac OS 9 to allow
it to be booted in the "classic environment" within
Mac OS X. This is a compatibility layer in Mac OS X (in
fact a Mac OS X application, originally codenamed the "blue
box") that runs a complete Mac OS 9 operating system,
so allowing applications that have not been ported to Carbon
to run on Mac OS X. This is reasonably seamless, though
"classic" applications retain their original Mac
OS 8/9 appearance and do not gain the Mac OS X "Aqua"
appearance.
- Mac OS 9.0
- Mac OS 9.0.2
- Mac OS 9.0.3
- Mac OS 9.0.4
- Mac OS 9.1
- Mac OS 9.2
- Mac OS 9.2.1
- Mac OS 9.2.2
Mac OS X
Mac OS X (pronounced /mæk oʊ ɛs tɛn/) is the line of
graphical operating systems developed, marketed, and sold
by Apple Inc. which succeeded the original Mac OS, which
had been Apple's primary operating system since 1984. Unlike
the earlier Macintosh operating system, Mac OS X is a Unix-based
operating system[9] built on technology developed at NeXT
from the second half of the 1980s until early 1997, when
Apple purchased the company.[10]
The first version was Mac OS X Server 1.0 in 1999, which
retained the earlier Mac operating system's "platinum"
appearance and even resembled OPENSTEP in places. The desktop-oriented
version, Mac OS X v10.0, followed in March 2001 sporting
the new Aqua user interface. Since then, five more distinct
"end-user" and "server" versions have
been released, most recently Mac OS X v10.5 in October 2007.
Releases of Mac OS X are named after big cats; for example,
Apple calls Mac OS X v10.5 "Leopard," while its
previous release was called "Tiger."
Versions of Mac OS X:
- Mac OS X v10.0 (Cheetah)
- Mac OS X v10.1 (Puma)
- Mac OS X v10.2 (Jaguar)
- Mac OS X v10.3 (Panther)
- Mac OS X v10.4 (Tiger)
- Mac OS X v10.5 (Leopard)
- Mac OS X v10.6 (Snow Leopard)
Timeline

Click image to view full version
Star Trek
One interesting historical aspect of the classic Mac OS
was a relatively unknown secret prototype Apple started
work on in 1992, code-named "Star Trek" (as in
"to boldly go"). The goal of this project was
to create a version of Mac OS that would run on Intel-compatible
x86 personal computers. The project was instigated by Novell,
Inc., who were looking to integrate their DR-DOS with the
Mac OS UI as a retort to Microsoft's Windows 3.0. The Apple/Novell
team (fourteen engineers from the former, four from the
latter) was able to get the Macintosh Finder and some basic
applications, like QuickTime, running smoothly on a PC.
Some of the code from this effort was reused when porting
the Mac OS later to PowerPC.
The project was short lived, being canceled only one year
later in early 1993. There are two theories for the cancellation:
the first is that Apple's board deep-sixed further development
upon realising that going with Star Trek would mean an entirely
new business model and one that would likely see a notable
drop in Apple's lucrative hardware sales; and the second
is that an x86 Mac OS was not commercially viable in the
early nineties because Microsoft's contracts for Windows
3.1 forced PC manufacturers to pay a royalty to Microsoft
for every computer shipped, regardless of what operating
system it contained.
A further complication was that Star Trek was designed
to be source-level compatible, not binary compatible, with
the Mac OS. Mac applications would therefore have to be
recompiled or rewritten by their developers to run on the
x86 architecture, and there was much skepticism as to exactly
how much work this would entail.
Fifteen years after Star Trek, support for the x86 architecture
was officially included in Mac OS, and then Apple transitioned
all desktop computers to the x86 architecture. This was
not the direct result of earlier Project Star Trek efforts.
The Darwin underpinning used for Mac OS X 10.0 and later
included support for the x86 architecture. The remaining
non-Darwin portion of Mac OS X (based on OPENSTEP, which
ran on Intel processors) was released officially with the
introduction of x86 Macintosh computers.
68000 emulation
Although the Star Trek software was never released, third-party
Macintosh emulators, such as vMac, Basilisk II, and Executor,
eventually made it possible to run the classic Mac OS on
Intel-based PCs. These emulators were restricted to emulating
the 68000 series of processors, and as such most couldn't
run versions of the Mac OS that succeeded 8.1, which required
PowerPC processors. Most also required a Mac ROM image or
a hardware interface supporting a real Mac ROM chip; those
requiring an image are of dubious legal standing as the
ROM image may infringe on Apple's intellectual property.
A notable exception was the Executor commercial software
product from Abacus Research & Development, the only
product that exclusively used 100% reverse engineered code
without the use of Apple technology. It ran extremely fast
but never achieved more than a minor subset of functionality.
Few programs were completely compatible and many were extremely
crash-prone if they ran at all. Executor filled a niche
market for porting 68000 classic Mac applications to x86
platforms; development ceased in 2002 and the project is
now defunct.
Emulators using Mac ROM images offered near complete Mac
OS compatibility and later versions offered excellent performance
as modern x86 processor performance increased exponentially.
Unfortunately most of the Mac user base had already started
moving to the PowerPC platform that offered excellent classic
Mac backward compatibility on 8.xx & 9.xx operating
systems along with faster PowerPC software support. This
helped ease the transition to PowerPC-only applications
while prematurely obsolescing 68000 emulators and the Classic-only
applications they supported well before these emulators
were refined enough to compete with a real Mac.
PowerPC emulation
At the time of 68000-emulator development PowerPC support
was difficult to justify not only due to the emulation code
itself but also the anticipated wide performance overhead
of an emulated PowerPC architecture vs. a real PowerPC based
Mac. This would later prove correct with the start of the
PearPC project even years later despite the availability
of 7th & 8th generation x86 processors employing similar
architecture paradigms present in the PowerPC. Many application
developers were also creating and releasing both 68000 Classic
and PowerPC versions concurrently helping to negate the
need for PowerPC emulation. PowerPC Mac users who could
technically run either obviously chose the faster PowerPC
applications. Soon Apple was no longer selling 68000-based
Macs and the existing installed base started to quickly
evaporate. Despite the eventual excellent 68000-emulation
technology available they proved never to be even a minor
threat to real Macs due to their late arrival and immaturity
even several years after the release of much more compelling
PowerPC based Macs.
The PearPC emulator is capable of emulating the PowerPC
processors required by newer versions of the Mac OS (like
Mac OS X). Unfortunately, it is still in the early stages
and, like many emulators, tends to run much slower than
a native operating system would.
During the transition from PowerPC to Intel processors,
Apple realized the need to incorporate a PowerPC emulator
into Mac OS X in order to protect its customers' investments
in software designed to run on the PowerPC. Apple's solution
is an emulator called Rosetta. Prior to the announcement
of Rosetta, industry observers assumed that any PowerPC
emulator running on an x86 processor would suffer a heavy
performance penalty (e.g., PearPC's slow performance). Rosetta's
relatively minor performance penalty therefore took many
by surprise.
Another PowerPC emulator is SheepShaver, which has been
around since 1998 for BeOS on the PowerPC platform, but
in 2002 was open sourced with porting efforts beginning
to get it to run on other platforms. Originally it was not
designed for use on x86 platforms and required an actual
PowerPC processor present in the machine it was running
on similar to a hypervisor. Although it provides PowerPC
processor support, it can only run up to Mac OS 9.0.4 because
it does not emulate a memory management unit.
Other examples include ShapeShifter (by the same programmer
that conceived SheepShaver), Fusion and iFusion. The latter
ran classic Mac OS with a PowerPC "coprocessor"
accelerator card. Using this method has been said to equal
or better the speed of a Macintosh with the same processor,
especially with respect to the m68k series due to real Macs
running in MMU trap mode, hampering performance.
Macintosh clones
Several computer manufacturers over the years have made
Macintosh clones capable of running Mac OS, notably Power
Computing, UMAX and Motorola. These machines normally ran
various versions of classic Mac OS. Steve Jobs ended the
clone-licensing program after returning to Apple in 1997.
In 2008, a manufacturing company in Miami, FL called Psystar
Corporation, announced a $499 clone that comes with a barebones
system that can run Mac OS X 10.5 Leopard. Threatened with
legal battles, Psystar originally called the system OpenMac
and have since changed it to Open Computer.
A/UX
In 1988, Apple released its first UNIX-based OS, A/UX,
which was a UNIX operating system with the Mac OS look and
feel. It was not very competitive for its time, due in part
to the crowded Unix market. A/UX had most of its success
in sales to the U.S. government, where UNIX was a requirement
that Mac OS could not meet.
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