ASROCK X300TM-ITX Handbuch Seite 17

It is not allowed to install a DDR, DDR2 or DDR3 memory module into a DDR4 slot;
otherwise, this motherboard and SO-DIMM may be damaged.
The SO-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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X300TM-ITX
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