Processor and memory Like the Macintosh 128K before it, the 512K contained a
Motorola 68000 connected to 512
KB of
DRAM by a
16-bit data bus. Though the memory had been quadrupled, it could not be upgraded. The large increase earned it the nickname
Fat Mac. 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. This shared arrangement reduces CPU performance by up to 35%. It shared a revised logic board with the rebadged Macintosh 128K (previously just called the Macintosh), which streamlined manufacturing. The resolution of the display was the same at 512 × 342. Apple sold a memory upgrade for the Macintosh 128K for $995 initially, and reduced the price when 256
Kb DRAM prices fell months later.
Software 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 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 printer became available shortly after the 512K's introduction, as well as the number pad, mic, tablet, keyboard, mouse, basic mouse, and much more. It utilized Apple's built-in networking scheme
LocalTalk which allows sharing of devices among several users. The 512K was the oldest Macintosh capable of supporting Apple's
AppleShare built-in file sharing network, when introduced in 1987. The expanded memory in the 512K allowed it to better handle large word-processing documents and make better use of the graphical user interface and generally increased speed over the 128K model. Color Systems Technology used an army of 512K units connected to a custom
Intel 80186-based machine to colorize numerous black-and-white films in the mid-1980s.
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. ==Upgrades==