4x DDR4 (2666 MHz, up to 4400 MHz via overclocking). The Features of the ASUS Maximus XI HERO Motherboard at a Glance The ASUS Maximus XI HERO in Detail Using the cutting edge i9-9900K processor, the ASUS Maximus XI HERO natively supports speeds of up to 2666 MHz, and up to 4400 MHz with overclocking.
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