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i have bought imac 27 2013 I5-4570. can i upgrade cpu i7-4770k? plz help me

From the same model yes ( 22 nm “Haswell” Quad Core 3.5 GHz Intel “Core i7” (4771) processor ) - any old/new i7? No. If you use a processor never installed as a OEM processor you’ll have extension (aka driver) issues, you may also have EFI (aka bios) issues. If this answer is acceptable please remember to return and mark it accepted.

Don´t know about the i7-4770k, but I replaced the i5-4570 for an i7-4771 and it worked fine. I tried with the i7-4790 as well but that one wasn’t compatible.