Stefan Mileschin

Now that both Samsung and Micron are shipping their 16 Gb DDR4 memory chips to third parties, we're seeing wider availability of 32 GB unbuffered memory modules (UDIMMs). To date, six brands have either introduced, or started to sell their 32 GB unbuffered DIMMs, and in the coming months more manufacturers are expected to follow.
The Basics

Before we proceed, let us recap the basics here. Because of the way memory sub-systems work, high-capacity memory modules (in our case, 32 GB and higher) for workstations and servers are built differently than regular DIMMs for client PCs (which are called unbuffered DIMMs, or UDIMMs). Registered DIMMs (RDIMMs) carry a register chip that buffers the address and command signals, whereas the Load Reduced DIMMs (LRDIMMs) replace the register with an Isolation Memory Buffer that buffers the command, address, and data signals. While both the register chip and the IMB allow hardware vendors to build high-capacity memory modules and memory subsystems, neither RDIMMs nor LRDIMMs work with regular client platforms. Therefore, if you use a contemporary desktop and need a lot of memory for some reason, you'll need 32 GB UDIMMs.

You can read more about contemporary types DIMMs an appropriate article covering different types of contemporary memory modules

At the time of writing, 32 GB UDIMMs are supported by client platforms based on AMD’s 400 and 500-series chipsets as well as Intel’s 300-series chipsets.
The List

Twitter user momomo_us, who is from Japan, has managed to get a list of 32 GB unbuffered memory modules that are either available now or are about to hit the shelves there. The list is valid for Japan, yet we do know that ADATA and G.Skill are about to launch their 32 GB UDIMMs in the near future too, so our list includes data on these memory sticks as well.

There are a number of remarks to be made about 32 GB memory modules. Samsung’s mass-produced 16 Gb DDR4 memory chips are rated for 2133 MT/s, 2400 MT/s, and 2666 MT/s data transfer rates, yet even the company itself sells 32 GB DDR4-2933 memory modules. Meanwhile, its partners go all the way to DDR4-3000, albeit at 1.35 Volts. Meanwhile, the only modules that semiofficially feature Micron’s 16 Gb DDR4 chips are rated at 2400 or 2666 MT/s, at 1.2 Volts.

https://www.anandtech.com/show/14680...d-dimms-listed