Unraveling the Mystery: What Did the Turbo Button Do on Old Computers?

As technology advances at a breakneck pace, it’s easy to forget the innovations that laid the groundwork for our current digital landscape. In the realm of vintage computers, one intriguing feature that continues to pique curiosity is the turbo button. So, what did the turbo button do on old computers? This article explores its purpose, function, and relevance in the early days of computing.

The Purpose of the Turbo Button

Back in the 1980s and early 1990s, the turbo button was a common sight on many personal computers, particularly those using the IBM PC architecture. The button’s primary function was to switch the computer’s central processing unit (CPU) between two different speeds. Contrary to popular belief, the turbo button was not designed to increase the computer’s performance but rather to slow it down.

The need for this feature arose as computer hardware advanced rapidly, outpacing the software available at the time. Older software, including games and applications, was programmed to run at specific clock speeds. As newer computers with faster processors hit the market, these older programs would run too quickly or become unstable.

Enter the turbo button, which allowed users to toggle between the computer’s maximum speed and a slower, more compatible speed. This compatibility mode enabled older software to run at a pace close to what the developers had initially intended, ensuring smoother performance and fewer crashes.

How the Turbo Button Worked

The turbo button was typically connected to the motherboard via a two-pin connector. Pressing the button would send a signal to the motherboard, which in turn would adjust the clock multiplier, bus speed, or both, depending on the system’s design. This change in speed would be reflected on a small LED display on the front of the computer case, indicating the current clock speed.

For example, a computer with an Intel 80286 processor running at 12 MHz might have a turbo button that switched between 12 MHz (full speed) and 8 MHz (compatible mode). The slower speed would allow the system to better handle software designed for the IBM PC XT, which had an Intel 8088 processor running at 4.77 MHz.

The Disappearance of the Turbo Button

As technology continued to evolve, the need for the turbo button waned. The primary reasons for its disappearance are twofold:

  1. Improved Software Compatibility: Over time, developers adapted to the rapid advancements in hardware, implementing better programming practices to ensure their software could run on a wider range of systems. This reduced the need for users to toggle between different CPU speeds to achieve compatibility with older programs.
  2. Processor Speed Throttling: Modern CPUs feature dynamic frequency scaling, also known as CPU throttling. This technology allows the processor to adjust its clock speed in real-time based on system demand, power consumption, and thermal constraints. This dynamic approach to speed management rendered the turbo button obsolete, as the CPU could now automatically accommodate the varying performance requirements of different software.

With the decline in demand for the turbo button, computer manufacturers gradually phased it out, and by the late 1990s, it had all but disappeared from new systems.


The turbo button on old computers served as a practical solution to the problem of hardware outpacing software. By allowing users to switch between a faster and slower CPU speed, the turbo button ensured compatibility with older software, offering a smoother and more stable computing experience. As technology progressed and software adapted, the need for the turbo button diminished, leading to its eventual disappearance from modern systems. While the turbo button may now be a relic of the past, its legacy lives on as a testament to the ingenuity and adaptability of early computer engineers.

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