ASRock has released a new firmware (Version 1.4) for its X299 Taichi CLX motherboard that brings support for RDIMMs (registered DIMMs). Standard DIMMs currently max out at 32GB per stick. RDIMMs, on the other hand, hold up to 256GB on a single module. However, there are two caveats.
For starters, RDIMM support is solely coming to the Intel Skylake-X family of processors. For reasons unknown, ASRock couldn't get the modules to work with Intel's Skylake-X Refresh or Cascade Lake-X chips. Secondly, although the X299 Taichi CLX will boot with RDIMMs, they will only operate if it's not in ECC (error-correcting code) memory mode.
As overclocking extraordinaire Nick Shih has proven, the biggest benefit to RDIMMs is the possibility of having huge amounts of RAM on a high-end desktop (HEDT) platform, which natively supports up to 256GB of DDR4 RAM. Yes, you do lose out on ECC functionality, but you're getting more memory without having to step over to the enterprise side of components.
Shih ran eight 128GB LRDIMMs (load-reduced DIMMs) on his X299 Taichi CLX motherboard. We can't wait until someone breaks through that 1TB ceiling.