Several years ago, we toyed with the idea of doing a fresh OS install directly to DRAM, by adding a "Format RAM" option to a BIOS.
Today, I appended the following Comment at that ExtremeTech article:
DDR4-2666 x 8 ~= 21,328 MB/second (raw bandwidth)
Compare a PCIe 4.0 "4x4" add-in card e.g. upgraded ASRock Ultra Quad M.2 Card:
16G / 8.125 x 4 PCIe 4.0 lanes x 4 Gen4 NVMe M.2 ~= 31,507 MB/second (raw bandwidth)
As such, instead of formatting Optane DIMMs for a fresh OS install,
PCIe 4.0 offers superior raw bandwidth for an OS installed on such a "4x4" card.
And, according to ASRock's published documentation, multiple Ultra Quad M.2 cards can be installed in a single motherboard.
Actual performance then depends a lot on the M.2 drives installed on such a card.
Also, Gen4 M.2s are expected to become more plentiful in the next few months,
and the competition among same should help drive prices down.
Thus, it should be easy to compare Gen4 M.2 Optanes with other Gen4 M.2 drives
in a "4x4" add-in card e.g. if latency is a major consideration.
p.s. I haven't looked: has Intel announced a Gen4 M.2 Optane yet?
At Newegg today, only Corsair, Gigabyte and XPG are selling Gen4 M.2s: