Back in the 486 days, it was common to see a “Turbo” button on the front panel of many PCs, which was used to toggle between the CPU’s maximum speed and a slower clock rate that was sometimes necessary for compatibility with older software. Usually an LED would light up to show you were running at this higher speed, or if your machine was very fancy, it might even have a numerical display that would show the current CPU frequency.
Just like the frequency indicators of yore, the Arduino doesn’t actually measure the CPU’s frequency, it’s simply reading the state of the Turbo LED on the front panel. When the LED is off the Arduino shows an image of a i8088 CPU on the screen to indicate the computer is running in compatibility mode, and when the LED is on, the screen shows the Cyrix Cx486 DX2 logo. When the button hasn’t been pressed in awhile, the display defaults to a star field screensaver.
Regular readers may recall we recently covered a similar project that used an Arduino to add a little flair to an era appropriate seven-segment LED display. We’d say there’s still a good deal of romanticism about computers having a big “TURBO” button you can smash whenever you feel the need for speed.
Source: OLED DISPLAY LETS VINTAGE PC ENGAGE TURBO MODE IN STYLE