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 was quadrupled from the original. 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 drive
 * First supported OS: System 1.1
 * Last supported OS: System 4.1

Upgrade paths
A Mac 512K could be upgraded to a 512Ke (enhanced) through the Macintosh Plus Disk Drive Kit (part no. M2516), which included new 128KB ROMs (to replace the 64KB version), an 800KB floppy drive (to replace the 400KB drive), and a Macintosh Plus System Tools disk with installation guide. The upgrade allowed older 512K systems gain many of the same features of the Macintosh Plus for a fraction of the price. An upgrade involving only a ROM swap was also available, but did not include the 800KB floppy drive. The original 128K Macs are not capable of taking advantage of this upgrade kit without first installing more RAM.

A Mac 512K could also be upgraded to a Macintosh Plus through the more costly Macintosh Plus Logic Board Kit (part no. M2518) from Apple, which included a new logic board with the 128KB ROMs, 1MB memory, SCSI port, and a replacement rear case. An extended Mac Plus keyboard was available separately (part no. M2519).