A Bad Apple?

As fans of vintage computing equipment know, a lot of intrigue and a great many myths surround the events and individuals that shaped the early personal computing revolution. Perhaps some of the best tales come from the storied beginnings of Apple Computer. People love to hear the stories of the co-founders, Steve Jobs and Steve Wozniak, designing and building the first Apple computers in the garage of Jobs’ parents’ home. But truth be told, it never really happened that way.

Sorry to burst your bubble, but Wozniak has made it clear that this garage was little used, and played almost no role in getting the company started, despite the fact that the location is treated like a shrine by many Apple enthusiasts to this day. While there is clear evidence available to debunk this myth, not all matters can be settled so easily.

It has long been suspected that the Apple IIGS, first released in 1986, was intentionally hamstrung by Steve Jobs so that it would not take the spotlight off of his pet project, the Macintosh. The IIGS was meant to be a major upgrade over the 8-bit Apple II computers of the past, with a more powerful, 16-bit 65C816 CPU. But while this chip could likely outperform the Motorola 68000 running at an effective rate of 6 MHz in the Macintosh even when running at a somewhat lower clock speed, the 65C816 was limited to just 2.8 MHz.

This creates something of a mystery, because GTE was producing 65C816 chips that ran at 4 MHz at the time, and most IIGS machines had them installed. Furthermore, there were no technical issues, like memory access speed, that would have prevented the system from being clocked at 4 MHz. So was it really an intentional plot to slow the machine down? YouTuber Userlandia recently took a very deep dive into the topic to see where the evidence led.

After running down information from numerous sources, it would appear that this was most likely not the case. Sorry conspiracy theorists, but you are wrong on this one! There are many reports of issues with the GTE 65C816 chips in the early days of their production. They simply could not produce enough chips to supply a large customer like Apple with consistently reliable operation.

One reason for this was the REP and SEP opcodes, which set and reset flag bits of the CPU’s status registers. These opcodes were integral to switching between 8- and 16-bit modes, which was necessary for backwards compatibility with the existing Apple software library. The instructions were problematic at higher speeds due to some design flaws, which would prevent them from completing within the allotted number of clock cycles.

So the most likely reason the IIGS was clocked down was to provide a stable environment for these not-so-stable early processors. Further evidence for this theory is provided by the existence of 3 MHz chips installed in some IIGS computers. These variants were not referenced in any official GTE documentation, so it is suspected that they were actually 4 MHz chips that did not make the cut.

The full video has lots of interesting history and references many first-hand accounts that really breathe life into the events of the time. It is definitely worth the watch for retro computing enthusiasts.