CXL puts PCIe in competition with the DDR bus. The bandwidth was already there (now doubly so), but CXL brings the latency. That's exciting because the DDR bus is tightly linked to a particular memory technology and its assumptions -- assumptions which have been showing a lot of stress for a long time. The latency profile of DRAM is really quite egregious, it drives a lot of CPU architecture decisions, and the DDR bus all but ensures this tight coupling. CXL opens it up for attack.
Expect a wave of wacky contenders: SRAM memory banks with ultra low worst-case latency compared to DRAM, low-reliability DRAM (not a good marketing name, I know) where you live with 10 nines of reliability instead of 20 or 30 and in exchange can run it a lot faster or cooler, instant-persistent memory that blurs the line between memory and storage, and so on.
Thank, that it quite an interesting technology I wasn't aware of. Apparently Samsung already made a CXL RAM module for servers in 2021 (1). I wonder how Intel optane would have been if it had used CXL (assuming it didn't).
Side note but AMD devices' (laptops/NUCs) lack of thunderbolt or pcie access is why I'm quite hesitant to buy a portable AMD device which is quite unfortunate. I really hope AMD/their partners can offer a solution soon now that thunderbolt is an open standard.
Plenty of people are betting that future Optane will use CXL; it makes perfect sense. Sapphire Rapids doesn't support CXL.mem so we may have to wait for 4th gen Optane on Granite Rapids.
Expect a wave of wacky contenders: SRAM memory banks with ultra low worst-case latency compared to DRAM, low-reliability DRAM (not a good marketing name, I know) where you live with 10 nines of reliability instead of 20 or 30 and in exchange can run it a lot faster or cooler, instant-persistent memory that blurs the line between memory and storage, and so on.