Can I Use Registered ECC RAM with AM5 Motherboards?

If you're running 4 sticks of RAM, they should work, but you might not be able to use the overclock profiles due to AMD's official 3600MT/s support for 4 sticks of DDR5. If you can, consider just using 2 sticks for now and enjoy 64GB with overclocking options, keeping the extra for future use. Unfortunately, consumer-level motherboards don’t officially support ECC RAM, even though the DDR5 spec allows for it. You're likely to just be stuck at the standard speeds with no BIOS option for ECC enabled.

RDIMMs are exclusive to Threadripper and EPYC CPUs, and they won't work with AM5 boards. If you're unsure whether your RAM is RDIMM or UDIMM, it’s important to verify that because UDIMMs—despite having ECC capabilities thanks to DDR5 specs—are not registered and should work fine. If the capacity isn't crucial, think about just using 2x32GB sticks and selling the remaining ones. This way, you'll maximize speed and compatibility without losing out.

If the RAM you have is registered (RDIMM), you're out of luck with AM5; they don't support it at all. The AM5 platform is limited in terms of ECC support to keep costs down, so businesses have to pay for the more expensive options. You might want to check if your memory is indeed RDIMM or possibly UDIMM, which can work if they have on-die ECC—those should be fine on AM5. Otherwise, consider selling the RAM to fund a good 64GB XMP/EXPO kit instead.