One of the best ways to see how much headroom a manufacturing process has is to see how far you can overclock a chip with normal cooling and at default core voltages, so we did just that on these four CPUs. The results are as follows:

Athlon XP 2200+ (1.80GHz) - The highest we could overclock this core at default core voltage with AMD's recommended heatsink/fan was 1822.5MHz using a 135MHz FSB.
Athlon XP 1900+ (1.60GHz) - We managed to increase the clock multiplier and the FSB to 12.5x and 140MHz respectively, resulting in a 1750MHz overclocked frequency.
Athlon XP 1800+ (1.53GHz) - The 1800 made it to 1.60GHz, the speed of a 1900+ without any effort.
Athlon XP 1700+ (1.47GHz) - The 1700 made it to 1.53GHz, the speed of an 1800+.


It seems as if the Thoroughbred core needs some time to mature at this point, let's see how far we took the CPUs at voltages as high as 1.850V. Again, we stuck to stock cooling:

Athlon XP 2200+ (1.80GHz) - The Athlon XP 2200+ wouldn't go any further, 1822.5MHz was its peak.
Athlon XP 1900+ (1.60GHz) - We managed to increase the clock multiplier and the FSB to 12.5x and 150MHz respectively, resulting in a 1875MHz overclocked frequency.
Athlon XP 1800+ (1.53GHz) - Our best overclock out of the batch took us to a 12.5x multiplier with a 145MHz FSB which left us with a 1813MHz processor.
Athlon XP 1700+ (1.47GHz) - The 1700+ made its way up to 1.67GHz, the speed of a XP 2000+.