It is the first update of the original Macintosh 128K. It is virtually identical to the previous Macintosh, differing mainly in the amount of built-in RAM. The increased memory made the Macintosh a more capable computer for businesses and provided the ability to run more software.

The Macintosh 512K originally shipped with Macintosh System 1.1, but could run all versions of Mac OS up to and including System 4.1. It was replaced by the Macintosh 512Ke and the Macintosh Plus. All support for the Mac 512K ended on September 1, 1998.