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Macintosh 512K
Mac512K wb.jpg
Release date September 10, 1984
Introductory price $2795
Discontinued April 14, 1986
Operating system 1.0, 1.1, 2.0, 2.1, 3.0, 3.2[1], 3.3, 3.4, 4.0, 4.1
CPU Motorola 68000 @ 8 MHz
Memory 512 KB (built-in)
Mac 512K back panel

The Macintosh 512K Personal Computer, the second of a long line of Apple Macintosh computers, was the first update to the original Macintosh 128K. It was virtually identical to the previous Mac, differing primarily in the amount of built-in memory (RAM), which quadrupled the original's. This large increase earned it the nickname Fat Mac. The additional memory was significant because more ambitious users with computer experience stretched the capacity of the original Mac almost immediately, despite the limited number of applications.



Processor and memory

Like the 128K Macintosh before it, the 512K contained an 8 MHz Motorola 68000 connected to a 512 KB DRAM by a 16-bit data bus. Though the memory had been quadrupled, it could not be upgraded. A 64 KB ROM chip boosts the effective memory to 576 KB, but this is offset by the display's 22 KB framebuffer, which is shared with the DMA video controller. It shared a revised logicboard with the re-badged Macintosh 128K (previously just called the Macintosh), which streamlined manufacturing.


The applications MacPaint and MacWrite were still bundled with the Mac. Soon after this model was released, several other applications became available, including MacDraw, MacProject, Macintosh Pascal and others. In particular, Microsoft Excel, which was written specifically for the Macintosh, required a minimum of 512 KB of RAM, but definitively solidified the Macintosh as a serious business computer. Models with the enhanced ROM also supported Apple's Switcher, allowing cooperative multitasking among (necessarily few) applications.

New Uses

The LaserWriter became available for the first time shortly after the 512K's introduction, making home desktop publishing a possibility for the first time, although the LaserWriter's initial US$6,995 price put it far out of the reach of most individuals. It utilized Apple's built-in networking scheme LocalTalk which made it more affordable shared among several users. In addition, the 512K became the earliest Mac capable of supporting Apple's AppleShare built-in file sharing network, when introduced in 1987. More importantly the expanded memory in the 512K allowed it to better handle large word-processing documents and take better use of the graphical user interface and generally increased speed. In particular, combined with the LaserWriter, the introduction of Aldus Pagemaker software, which took full advantage of the extra RAM, revolutionized the publishing industry and solidified the Macintosh as the de-facto desktop publishing computer.

System software

The original 512K could accept Macintosh system software up to version 4.1; System Software 5 was possible if used with the Hard Disk 20; With the OEM 800K Drive and ROM upgrade kit a 512Ke could accept up to System 6.0.8.


An updated version replaced the Mac 512K and debuted as the Macintosh 512K enhanced in April 1986. It differed from the original 512K in that it had an 800 KB floppy disk drive[2] and the same improved ROM as the Macintosh Plus. With the exception of the new model number (M0001E), they were otherwise cosmetically identical. The stock 512K could also use an 800 KB floppy disk drive as well as the Hard Disk 20, the first hard disk manufactured by Apple exclusively for use with the 512K, but required a special system file (not required by the 512Ke) that loaded the improved ROM code into RAM, thus reducing the available RAM for other uses. Apple offered an upgrade kit which replaced the floppy disk drive and ROMs essentially turning it into a 512Ke. One further OEM upgrade replaced the logicboard and the rear case entirely with that of the Macintosh Plus.

However, unlike the Macintosh 128K, the 512K had enough RAM to make use of many third party developer solutions for tapping into the 68000 processor since Apple made no provision for an upgrade card. These included "snap-on" SCSI cards, internal hard drives and RAM upgrades of as much as 2 MB or more.


Timeline of compact Macintosh models

See also


  1. ^ System Software: Configs for Mac 128K, XL, 512, & 512KE (7/94)
  2. ^ Apple Inc. (August 22, 1991). "Double-Density Versus High-Density Disks". Article ID: 3802. Apple Inc.. Retrieved 2008-06-28.   "This article gives the specifications for the 800K floppy disks and the 1.44 MB floppy disks." 800K Disk has 1600 sectors and 1.44 MB Disk has 2880 sectors. A sector is 512 bytes.

External links


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