Macintosh Plus

The **Macintosh Plus** is a personal computer that was designed, manufactured, and sold by Apple Computer from January 1986 to October 1990. Introduced two years after the original Macintosh, it was the third model in the Macintosh line and featured several hardware improvements over its predecessor, the Macintosh 512K.

## Overview

The Macintosh Plus shipped with 1 MB of RAM (expandable to 4 MB via four 30-pin SIMM slots), a new 800 KB floppy drive with two sides, and a SCSI port. The SCSI interface allowed the system to connect to external hard drives, printers, scanners, and other peripherals, the first time Apple had done this.

It was also the first Macintosh to support the HFS for more complex file management.

## Features

The Macintosh Plus introduced some improvements including a SCSI port for external devices, 1 MB of RAM, and an 800 KB double-sided floppy disk drive.

Its improved RAM capacity allowed it to run more demanding software, and the SCSI port made it popular in desktop publishing and business applications.

## Design

The Plus maintained the all-in-one form factor like the computers before it, with a 9-inch monochrome display and small size. It came bundled with a keyboard featuring arrow keys and a numeric keypad.

Like earlier models, the Macintosh Plus didn't have an internal fan, which made it quieter than competing PCs but also prone to overheating.

On the inside of the case, the names of the original Macintosh development team were molded into the plastic, including Steve Jobs, Andy Hertzfeld, and Susan Kare.

## Software

The Macintosh Plus originally shipped with System Software 3.0 and Finder 5.1, and it remained compatible up to System 7.5.5. It included software bundles, such as MacPaint and MacWrite, HyperCard, Microsoft Excel (first released on Macintosh), and Aldus PageMaker.

## Upgrades and compatibility

Apple offered a factory upgrade kit for owners of earlier Macs (128K or 512K), allowing them to convert to a Plus by replacing the motherboard, floppy drive, and back case.

Some third-part developers released accelerators and memory expansions that pushed RAM up to 16 MB; far above Apple’s official 4 MB maximum.

## Known issues

Early Macintosh Plus units had a SCSI bug that would prevent booting when external devices were not powered correctly.

The lack of a cooling fan led to overheating in some units, with long-term strain on analog board solder joints and power supply failures being common.

## Legacy

The Macintosh Plus was in production for nearly five years, longer than any other Macintosh until the second-generation Mac Pro (2013–2019). It was a common to see one at schools and universities throughout the late 1980s.

Some educational units were sold under the name "Macintosh Plus ED" for institutional use.

## Other websites

- Official Apple specifications
- Macintosh Plus Developer Note (PDF)
- Folklore.org: Macintosh team stories
- Macintosh software archive
- EveryMac: Macintosh Plus Specs

## Infobox (computer)

- **name**: Macintosh Plus
- **logo**:
- **manufacturer**: Apple Computer
- **type**: All-in-one computer
- **price**: US$2,599
- **cpu**: Motorola 68000 @ 7.8 MHz
- **memory**: 1 MB RAM (expandable to 4 MB)
- **display**: 9-inch monochrome, 512 × 342 pixels
- **os**: System Software 3.0–7.5.5
- **predecessor**: Macintosh 512K
- **successor**: Macintosh SE