In 1975, IBM released the first mass-produced portable computer, the 5100.

It was an incredible feat for the time: An integrated 5-inch CRT monitor, up to 64 kilobytes of random-access memory (RAM), and the ability to run programs meant for larger, more expensive computers, all in something the size of a briefcase.

In fact, the IBM 5100 was extraordinarily close to becoming the world’s very first Personal Computer, a title taken a few short months earlier by the Altair 8800.

But the IBM 5100 was more than just a portable computer. It contained a hidden feature that remained undiscovered by the general public for fifteen years, until the year 2000.

The year John Titor supposedly arrived on our world-line.

2036

John Titor’s story began in the year 2036.

Titor belonged to a team of seven individuals selected to embark on a journey through time. He had lived through unimaginable horrors in a world destroyed by selfishness, cynicism, and corrupt government, ravaged by nuclear war.

To make matters worse, what little remained of their technology was threatened by a looming UNIX timeout error in 2038.

An IBM 5100 was just what they needed. It’s ability to debug and emulate code between various programming languages made it an important component in keeping the technological architecture of their fallen world alive.

Unfortunately, none could easily be found in 2036.

And so Titor’s mission was straightforward: Travel to 1975, using a rudimentary time machine, and acquire an IBM 5100 portable computer.

IBM 5100 To The Rescue

While this is only one very small part of the John Titor legend, it seems to be the genesis for the entire myth. Looking at it as a story, without the 2038 timeout and the need for an IBM 5100, Titor would have never been sent on his mission through time.

And what’s interesting is, for all intents and purposes, time travel notwithstanding, it’s very much grounded in reality.

We need the system to “debug” various legacy computer programs in 2036. UNIX has a problem in 2038. – John Titor

The IBM 5100 did, indeed, contain functionality that was hidden from the public. At a time when most computers could only support the BASIC programming language, the IBM 5100 had the ability to emulate programs in both BASIC for system/3 and APL for system/370 (the “system” in this case refers to IBM mainframes). According to Bob Dubke, one of the IBM 5100 engineers, this function was hidden “because of worries about how [IBM’s] competition might use it.”

That piece of the story is verifiably correct.

Even if the function weren’t hidden, however, the general public, especially around 2000-2001, most likely had little idea that such a machine even existed. Whoever the individual posting as John Titor was, he knew his stuff.

So, if the UNIX timeout of 2038 is to be a serious problem, and if in 2036 we require the ability to “reverse engineer” or debug certain code to prevent a technological apocalypse, a 5100 could be our go-to machine.

The Unix Timeout Of 2038

The UNIX timeout, by the way, is a very real concern.

A timeout error is caused by the way computers count system time. They count time not by actual dates — months, days, or years, as we do — but rather by seconds.

The problem is that computers also have a limit to how high they can count. So, when they reach that limit, various problems may occur.

The 2038 UNIX timeout in particular stems from the limitations of computers using signed 32-bit integers. Once these 32-bit, UNIX-based computers reach their limit at 03:14:07 UTC on Tuesday, January 19, 2038, they will encounter something called a 32-bit overflow.

From that point, the date on these machines will be interpreted as 1901.

This will cause operating systems and certain software to malfunction, unless we successfully prevent it from happening.

This issue isn’t only limited to UNIX-based computers, either, as any computer or software that relies on a 32-bit integer, as well as the UNIX epoch, will reach the same error (it should be noted that 64-bit machines, which are becoming more common these days, won’t suffer the 2038 UNIX problem).

The Y2K bug was surrounded by very similar circumstances, and such errors have even temporarily brought down commercial software and devices. The Microsoft Zune, for example, was the victim of a leap-year glitch, which caused Microsoft Zunes around the world to freeze at about 1:30 a.m. ET, Wednesday, December 31, 2008.

These errors, while troublesome, were clearly fixable. We’ve yet to see the implications of the UNIX timeout in 2038.

And that’s the thing about John Titor: Even though most of his “predictions” have proven false, like any good urban legend, his story contains many elements of truth. There’s even a profound moral message and warning: Change your ways, or things will go badly.

That, and maybe it’s time to upgrade your computer.