This message was posted on behalf of Intel Corporation
Thank you very much for contacting the Intel Communities Team, savelivio. I will be more than happy to assist you.
Allow me to mention that the Intel® Core™ I7-8700 processor will support DDR4-2666 memory (cf. Processor Datasheet, page 20-21/143). Although, you can install a DDR4 RAM of 3600 as long as the RAM module has a Serial Presence Detect chip on it (SPD). This chip will make the memory to run at the maximum frequency that the processor allows to.