ASROCK Z490M-ITX/ac Manual Del Usuario página 22

2.3 Installing Memory Modules (DIMM)
This motherboard provides two 288-pin DDR4 (Double Data Rate 4) DIMM slots,
and supports Dual Channel Memory Technology.
1. For dual channel configuration, you always need to install identical (the same
brand, speed, size and chip-type) DDR4 DIMM pairs.
2. It is unable to activate Dual Channel Memory Technology with only one memory
module installed.
3. It is not allowed to install a DDR, DDR2 or DDR3 memory module into a DDR4
slot; otherwise, this motherboard and DIMM may be damaged.
The DIMM only fits in one correct orientation. It will cause permanent damage to
the motherboard and the DIMM if you force the DIMM into the slot at incorrect
orientation.
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