Don't mix RDIMMs and UDIMMs. They won't work together.

No.

Registered (RDIMM) and unbuffered (UDIMM) memory are electrically incompatible. The T5810 can use either, but not both at the same time. If you plug in those cheap 32GB RDIMMs alongside your existing 16GB UDIMMs, the board will either not boot, or it will ignore one set entirely. There’s no “registered mode” that lets you mix and match — the memory controller expects one type per channel.

Your options: pull the UDIMMs and run only the RDIMMs, or stick with UDIMMs and skip the deal. The T5810 supports up to 64GB UDIMMs (4x16GB) or more with RDIMMs (up to 128GB or 256GB depending on CPU). Pick a lane.

Future You deserves memory that actually posts.