Macintosh 512K

The Macintosh 512K 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, which quadrupled the original's. This large increase earned it the nickname Fat Mac.

Specifications

 * CPU: 7.8336 MHz Motorola 68000
 * RAM: 512 KB
 * ROM: 64 KB
 * Drive: 1x 400 KB floppy disk
 * First supported OS: System 1.1
 * Last supported OS: System 4.1

Viewpoints
Although the "Fat Mac" packed four times as much memory as the 128K, it was not viewed as a real upgrade, until the Macintosh Plus came along.