Inside the Macintosh Plus

Introduction

Following the release of the original Macintosh in 1984 and the Macintosh 512K in 1985, Apple released the Macintosh Plus in 1986, now with 1 MB of RAM, an 800 kB 3.5” floppy disk drive, and a SCSI port. Let’s check it out.

The original Macintosh (Macintosh 128K), the Macintosh 512K, and the Macintosh Plus had the same basic design. Thus, we can consider these three models as the first generation of Macintosh computers. They were all based on the Motorola 68000 microprocessor, which was one of the most powerful CPUs available at the time, and had a 9-inch black-and-white video monitor with a resolution of 512 x 342 integrated on the computer’s body. The main difference between the three models is the amount of RAM (128 KB, 512 KB or 1 MB). However, while the first two models didn’t allow the user to add more memory, the Macintosh Plus uses SIMM-30 memory modules, allowing users to expand the memory up to 4 MB, as we will explain. In fact, in January 1988, Apple released models of the Macintosh Plus with 2 MB or 4 MB of RAM.

Another difference between the three models was with the floppy disk drive. The Macintosh 128K used a 400 kB 3.5” floppy disk drive. The first models of the Macintosh 512K (part number “M0001W”) also used a 400 kB 3.5” floppy disk drive, but later models (part numbers “M0001E” and “M0001D”) used an 800 kB 3.5” floppy disk drive. The Macintosh Plus came with an 800 kB 3.5” floppy disk drive.

None of these computers come with a hard drive, so the operating system and programs must have been loaded through floppy disks. All of the time, we see people listing first-generation Macs on eBay, saying that the computer is “defective” because the operating system is not loading and the computer is showing an icon with a floppy disk and a question mark. (The person selling the computer does not realize that old computers didn’t come with a hard drive.) This is the normal behavior of the computer when it doesn’t find a floppy containing the operating system, and it means the computer is working as expected.

The Macintosh Plus, however, was the first Macintosh computer to come with a SCSI port. This allowed you to install an external hard disk drive to this computer.

Originally, the Macintosh Plus was released in yellow, just like the Macintosh 128K and the Macintosh 512K. However, in January 1987, its color was changed to the light gray color (called “platinum”) that Apple started using on its computers from then on.

Figure 1: The Macintosh Plus

Nowadays, the first thing you will notice looking at the Macintosh Plus is how small it was. In Figure 2, we compare the Macintosh Plus to a 21-inch LCD monitor.

Figure 2: The Macintosh Plus compared to a 21-inch LCD monitor

Differently from the Apple II and Apple III, the keyboard was not part of the body of the computer. It was connected to the computer using a spiraled cable similar to the ones used by telephones. The keyboard was mechanical and almost identical to the one used with the Apple IIe, except that the old Open Apple and Solid Apple keys were replaced by the Command and the Option keys, respectively. The keyboard of the Macintosh Plus was different from the one used with the Macintosh 128K and the Macintosh 512K, as it now had a numeric keypad. The color was changed from yellow to platinum when the color of the Macintosh Plus changed (January 1987).

Figure 3: The keyboard

The mouse was rectangular with a single button, mechanically identical to the one used with the Macintosh 128K and the Macintosh 512K, which had its color changed from yellow to platinum when Apple changed the color of the Macintosh Plus. To this day, Apple mice still have only one button. It was connected to the computer through a DE-9 connector identical to the one used on the Macintosh’s serial ports, but the mouse port used a proprietary format.

Figure 4: The mouse