Macintosh 512K
The Macintosh 512K Personal Computer is the second of a long line of Apple Macintosh computers, and 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).
History
Soon after Apple introduced the Macintosh 128K they realized that the Macintosh would need more internal memory. Eight months later on September 10, 1984 Apple introduced the Macintosh 512K. With quadrupled RAM, the Macintosh was able to become a more business capable computer along with having the ability to run more software. The Mac 512K originally shipped with Macintosh System 1.1 but was able to run Macintosh System 1.0 all the way up to System 4.1. When the Macintosh Plus was introduced in 1986, the Macintosh 512K was discontinued on April 14, 1986. All support for the Mac 512K was discontinued on September 1, 1998.
Features
Processor and memory
Like the 128K Macintosh before it, the 512K contained a 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. This 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 re-badged Macintosh 128K (previously just called the Macintosh), which streamlined manufacturing. The resolution of the display was the same, at 512x342.
