Here is a quick overview of the front panel’s LEDs: Power LED Typically green in color and illuminated when the PC’s power is on.
Hard drive LED When the disk drive is seeking, reading, or writing data,
this red, orange, or amber LED is lit and flashes. The speed with which the
hard drive LED flashes is a good indicator of how busy your PC might be.
Typically, this LED is wired to the motherboard or the disk controller card
so that it reflects the activity of all disk drives on the PC.
Turbo LED If present, this yellow LED indicates that the PC is in turbo
mode. The turbo button was used on very early systems as part of a backward
compatibility strategy. There wasn’t a lot of software available to begin with,
and when the 8MHz systems were released, many people had a fair investment
in software that would run only in the older 4.77MHz, or PC XT mode. Normal
mode on these systems, 286 and 386 processors, was turbo mode. However,
when the turbo button was released, two things happened: the PC processor
was slowed to 4.77MHz and the turbo LED was turned off.Front-Panel Switches
Nearly all PCs now have at least one main switch, and many have two, on the front panel of
the PC. If there is only one switch, it is the main power switch. If there is another switch on
thefrontpanel,itistheresetswitch.Figure15-7showsaPCfrontpanelwithtwoswitches.(^348) PC Hardware: A Beginner’s Guide
Figure 15-7. The power and reset switches on a PC front panel