I remember setting those 7-segment LEDs up on my first PC build. On the motherboard there was a jumper which took the input from the turbo switch. To provide

I remember setting those 7-segment LEDs up on my first PC build. On the motherboard there was a jumper which took the input from the turbo switch. To provide feedback to the user, some cases ran a wire from the turbo switch to a bi-color LED on the front of the case as well as to the motherboard to control the turbo state. On fancier cases they had multiple seven-segment LEDs which had a multi-state jumper for each segment, which decided to light that segment depending if the switch was on or off (example: http://www.minuszerodegrees.net/led_speed_display/LED%20display%20-%20GK-01.jpg http://www.minuszerodegrees.net/led_speed_display/LED%20disp...), so you could display either the two different clock frequencies, or a "HI"/"LO" message, or anything you wanted. And connecting that switch input to the motherboard wasn't necessary for the LED to change, so I guess that is how your father's was setup :)