I know that overclocking can void your warranty, but what's the limit? Is it just a matter of increase clock speed at all, warranty void(I can understand this on normal processors)? If so, does the same go for the unlocked variants(K variants eg. i5 4690k)?
Please note that the warranty on Intel® processors will be void when the CPU frequency is changed. This can be either downclocking or overclocking the frequency.
Here you have a document about Intel® warranty information on processor: