Newegg High capacity 64gb (32x2) 3200mhz DDR4 on sale for $224.99.
(Timings are 16-18-18 which are the best available so far at this capacity)
Best price I've seen for these. Would allow you to store up to 256gb of DDR4 on a threadripper 8 dimm system, 128gb on a mainstream 4 dimm system, or...
I'm a bit out of my depth here, but I remember X99 had unofficial support for RDIMMS. Depends on a case by case basis though. I remember some posts here of users getting some 64gb dimms and I believe even 128gb dimms working on Asrock boards.
I bet there are some boards that do support greater...
Wanted to post one of Asrock's new ITX X570 boards that have been announced. Seems like the perfect fit for some interesting bifurcation builds. (Link)
4 sodimms (ecc support)
Dual 10gbe intel ports
Up to 8 sata 3 ports (via a breakout cable)
X570 chipset w/ pcie 4.0x16 slot (overclockable?)
True and CPU frequency too which makes it hard for apple to apple comparisons.
On another note, I think an interesting use case for such fast DDR4 would be if it were in quad channel on a threadripper setup. That would be some insane read write bandwidth. Wouldn't do much if any good for games...