3 Reasons DDR4 RAM Won't Work on a DDR5 Motherboard

The physical notch is in a different place DDR4 and DDR5 sticks have different keying, so a DDR4 module cannot physically fit into a DDR5 slot.

Voltage regulation and signaling are incompatible DDR5 motherboards use onboard voltage regulation and the CPU’s memory controller expects DDR5 signaling. DDR4 sticks cannot meet these electrical requirements.

Adapters claiming to convert DDR4 to DDR5 are scams No consumer adapter exists that can convert between the two standards. Any product sold as one is either a lie or a useless paperweight. Even if one existed, it would introduce latency and instability, costing more than just buying new RAM.