I'm not sure what you mean by ratio but the default clock multiplier for a 2000+ is 12.5, and the real clock speed is about 1.66 Ghz. The 2000+ is a preformance rating indicating that it will preform similary to a theoretical 2Ghz Thunderbird Athlon (and also a 2ghz P4).
How high it can overclock depends on many things including the processor stepping and quality of ram.