Inside the Apple III

Introduction

The Apple III (or, more correctly, Apple ///), codenamed “Sara,” was released in 1980 to be a “business” microcomputer. In this tutorial, we will take an in-depth look at its hardware and understand why it was Apple’s first failure.

There were three revisions of the Apple III. The first one presented an infamous stability problem, where the computer would crash for no apparent reason. Initially, it was thought that this was caused by overheating, as the Apple III didn’t have any fan and there was not enough space for air to circulate inside the machine. (The first computers from Apple didn’t have a fan because Steve Jobs thought fans were not elegant and produced noise; he wanted computers to be as quiet as possible. Fans were only added to Apple computers after he left the company.) The heat problem caused integrated circuits to pop from their sockets. It also created poor contact between the motherboard and the memory board, which didn’t use golden connectors as it should have. Another problem with the original Apple III was that its clock/calendar circuit simply didn’t work. This led to the infamous technical note where Apple recommended users facing problems with the Apple III to lift the computer two inches and drop it, as this would set the circuits back in place. This problem gave the Apple III a bad name and hurt sales, but it wasn’t the only reason why this computer wasn’t successful. (We will explore all of the reasons later.)

A revised version of the Apple III was released in early 1982, replacing all of the sockets and removing the clock/calendar circuit, which was now optional. Owners of the first revision could also replace their computers with the revised version for free. Whereas the original Apple III had 128 kB of RAM (+12 V chips), the revised version had 256 kB (+5 V chips). This is the model we are using in this tutorial.

Later, it was discovered that the problem was, in fact, with the motherboard manufacturing process, which was creating contacts were there shouldn’t have been any. A third version of the Apple III, called the Apple III Plus, was released with a new motherboard, which incorporated the clock/calendar circuit again. Its keyboard was yellow (the same color as the keyboard of the Apple IIe) instead of brown as on the previous versions. It was short-lived, as it was released in December 1983, and the entire Apple III line was officially discontinued in April 1984.

In Figure 1, you can see a “complete” Apple III system, with the computer at the bottom, its optional 5 MB external hard drive (“Profile”) in the middle, and its video monitor (“Monitor III”) at the top. The video output of the Apple III used the composite video format, so any composite video monitor would work with it; the Monitor III also worked with any device with composite video.

Figure 1: A “complete” Apple III system

In Figure 2, you can see the Apple III by itself.

Figure 2: The Apple III

The Apple III had a built-in 5.25”, 143 kB floppy disk drive. It ran an exclusive operating system called Apple SOS, which stands for Sophisticated Operating System. Apple wanted people to pronounce “SOS” as “sauce” (“apple sauce”), but the joke of calling it S-O-S after its big flop was unavoidable.