Hardware

The current product family of Macintoshes uses PowerPC processors, co-developed by Apple, IBM, and Motorola, and currently produced by IBM and Freescale, a former division of Motorola. All Macintosh models ship with 512 MB RAM standard, and as of October 12, 2005 the iMac G5 ships with the Apple Mighty Mouse, a two button mouse produced by Apple. Current Macintosh computers use the ATI Radeon or nVidia GeForce series chips for graphics, and include either a Combo Drive, a DVD player and CD burner all in one, or the Superdrive, a dual function DVD and CD burner. Macintoshes include two standard data transfer ports: USB, standardized in 1998 with the iMac, and FireWire, a less popular standard developed by Apple to support higher-performance devices.

Processor architecture

The original MC68000 was a 16/32-bit (32-bit internal) CISC processor that ran at 8 MHz in desktop systems, although the Macintosh Portable and PowerBook 100 both used a 16Mhz version. The Macintosh II featured a full 32-bit Motorola 68020 processor, but the Macintoshes at the time only supported 24-bit memory addressing, and so they only used a fraction of the chip's memory addressing capabilities. Macs with this limitation were referred to as '32-bit dirty'. The successor Macintosh IIx introduced the Motorola 68030 processor, which added an Memory Management Unit. The 68030 did not have a built in floating point unit, thus '030 based Macintoshes incorporated a separate unit - either the 68881 or 68882. Lower cost models did without, although they incorporated an FPU socket, should the user decide to add one as an option. The first '32-bit clean' Macintosh which could use 32-bit memory adressing was the IIci. Later, Apple released the Macintosh IIfx, which not only contained a 40 MHz 68030, but also two MOS Technology 6502 processors (the primary CPU in the older Apple II line) as auxiliary controllers. In 1991, Apple released the first computers containing the Motorola 68040 processor, which contained the floating point unit in the main processor. Again, lower cost models were FPU-less, being based on the cut-down Motorola 68LC040 instead.

Since 1994, Apple has been using the PowerPC line of processors, starting with the PowerPC 601, which were later upgraded to the 603 and 604. In 1997, Apple introduced their first computer based on the significantly upgraded PowerPC G3 processor; and followed it with the PowerPC G4 in 1999. The latest generation of processor in use is the 64-bit PowerPC G5, introduced in 2003. During the transition to the PowerPC, Apple wrote a 68030-to-PowerPC translation routine that booted very early in the OS loading. The first version of the OS to ship with the earliest PowerPC systems was estimated to be running 95% emulated. Later versions of the operating system increased the percentage of PowerPC native code, until OS X brought it to 100% native.

On June 6, 2005, Apple CEO Steve Jobs announced that the company would begin transitioning the Macintosh line from PowerPC to Intel microprocessors, with the transition expected to be complete by the end of 2007, and demonstrated a version of Mac OS X running on a computer powered by an Intel Pentium 4 CPU. Intel-powered Macs will be able to run Macintosh software compiled for PowerPC processors using a dynamic translation system known as Rosetta. The reason for this switch was problems with the power consumption of the IBM G5 processors, coupled with IBM's inability to deliver on the promised roadmap. Apple is expected to transition to Intel Pentium M processors in its Powerbook and iBook lines first (probably in June 2006), with the desktop lines following towards the second half of 2007. This future Macintosh architecture is informally called "Mactel", a reference to the Microsoft Windows-Intel colloquialism Wintel. During and for a time after the transition, developers are encouraged to compile and distribute universal binaries, which will run on both PowerPC and Intel-based Macs.

Expandibility and connectivity

The earliest form of Macintosh expandability was the Processor Direct Slot (PDS), present from the SE onwards. It was basically a shortcut to the CPU socket, not a bus - which also meant that parts for the PDS slot were tied to a specific Macintosh model, with the notable exception of the LC PDS slot, which was standardised across the entire LC line. The PDS slot could be used for processor upgrades, the Apple IIe Card, or video cards. The last line of Macintoshes to have PDS slots was the first generation of the PowerMacs. The first Macintosh to feature a bus for expansion was the Macintosh II in the form of six NuBus (a parallel 32-bit bus) slots. The NuBus was abandoned in favor of PCI in the second generation Power Macintoshes, and the G4 added an AGP slot for video cards. The latest G5s use PCI Express for graphics and expansion. For memory, Apple has used standard SIMMs (30- and 72-pin) and later DIMMs, with the notable exception of the Macintosh IIfx, which used special and very rare 64-pin SIMMs. Currently, the top-of-the-line G5 PowerMacs use 240-pin DDR2 SDRAM DIMMs.

The earliest Macintoshes used a special proprietrary serial port for external floppy or hard drives, until SCSI was introduced with the Macintosh Plus. SCSI remained the Macintosh drive connection of choice until the PowerMac G3, when cheaper EIDE drives became standard. Current PowerMacs use SATA for internal hard drives, EIDE for internal optical drives and FireWire for external drives. For peripherals, the Apple Desktop Bus was introduced with the Macintosh II. It was the standard input connector until the Universal Serial Bus was introduced with the iMac. The last Macintosh to have ADB was the blue and white PowerMac G3. Other legacy Macintosh peripheral connectors include the serial GeoPort and the AAUI port for networking. For external video signals, Apple used a DB-15 connector on all models prior to the blue and white G3, which uses a VGA connector, which was in turn dropped in favor of the Apple Display Connector with the PowerMac G4. On the most recent Macintoshes, Apple has used a standard or dual-link DVI connector.

From Wikipedia.