Basically there's 2x PIII models. The Coppermine are older (@1999) and the Tualatin is newer (@2001). Because of changes made in Tualatin cpus, they aren't compatible with Coppermine motherboards and vice-versa even though physically they fit. Either way the PIII was short lived due to serious issues and was quickly recalled. Finding a fully functional PIII isn't easy nowadays and with its processing speeds is limited in ability. You'd not notice any changes swapping the original cpu for something faster, unless you find the right cpu, which can be speeds of 1.1GHz or 1.4GHz and require very good cooling or run into constant thermal issues.