old pc's - turbo button?

[Van Hellseek]

just bought a full system for a fiver to have a play around with

it has a button marked "turbo" on the front of the case... what does it do?

 

[Bobbler]

Was to make older PCs run at a slower clock speed for compatibility with older software. Think it clocked them down to 25Mhz or maybe even 12Mhz when turbo was off !