The Macintosh Plus
In Figures 5 and 7, you have an overall look at the Macintosh Plus. Similarly to the Macintosh 128K and the Macintosh 512K, the Macintosh Plus had a brightness adjustment button on its front panel, below the Apple logo.
The Macintosh Plus is easy to identify as it has “Macintosh Plus” written on its front panel and on its rear panel as well. The original Macintosh had only “Macintosh” or “Macintosh 128K” (models manufactured after September 1984) written on its back, while the Macintosh 512K had “Macintosh 512K” written on its back.
Another way to differentiate the Macintosh Plus from the other first-generation models is through the computer’s part number, which was “M0001A.” The part number of the Macintosh 128K was “M0001” and the part number of the Macintosh 512K could be “M0001W” (for the original model with a 400 kB floppy disk drive), “M0001E” (for the 512Ke model, with an 800 kB floppy disk drive) or “M0001D” (for the 512Ke/800 model, with an 800 kB floppy disk drive and the same keyboard as the Macintosh Plus).
On the rear panel, the computer had a compartment for you to install a 4.5 V battery (known as TR133R, NEDA 1306A, 523, etc.) in charge of keeping the computer’s real time clock hardware working when the computer was turned off. Notice that this battery has the same physical size of a AA battery, but it is different (4.5 V vs. 1.5 V). In Figure 7, you can also see the optional anti-theft device installed. This device, which was also available for the Macintosh 128K and the Macintosh 512K, allowed the use of a steel cable to prevent people from stealing the computer, which was highly desirable in public spaces such as schools.
In Figure 8, you can see the connectors available at the rear panel of the Macintosh Plus. The first connector was a 3.5 mm jack for an external speaker (the computer had an internal speaker as well), followed by a proprietary mouse port, and a port for the installation of an external floppy disk drive. These ports were identical to the ones used on the Macintosh 128K and the Macintosh 512K.
The other ports available on the Macintosh Plus, however, were completely different.
There was an external 25-pin SCSI port, which allowed you to install an external SCSI hard disk drive to the Macintosh Plus. Therefore, the Macintosh Plus was the first Macintosh to support a hard disk drive, even though the computer didn’t come with one.
Then there were two serial ports, one for a printer and one for an external modem. The Macintosh 128K and the Macintosh 512K also had two serial ports, but with the Macintosh Plus, Apple changed the connector type used for them from DE-9 to DIN-8, which became the standard for future Apple computers.