The maximum clock frequencies just refer to the turbo frequencies, which is a stock feature, nothing to do with overclocking. There is no fixed "maximum" clock speed for overclocking. 7700Ks have been overclocked higher than 7 Ghz. But they don't need to be overclocked to be faster than the non-K version. The stock speed of the 7700 is 3.6 Ghz without turbo, 4.2 Ghz with turbo. The stock speed of the 7700K is 4.2 Ghz without turbo, 4.5 Ghz with turbo.