The notching on the m.2 ports / cards is supposed to denote if it’s SATA or NVME, all NVME capable slots are supposed to handle Sata as well. It’s similar to keying on other old expansion slots where the higher speed slot can accept either but the high speed card won’t fit in the low speed slot.
If I remember correctly part of the performance benefit is a reduction in the number of instructions required to read / write data which results in less overhead per file, a big deal if you have to move a million tiny files.
To comment on shoe size, I am a 12.5 4E meaning almost all shoes that exist will not fit my foot. I literally have two choices to wear in the most generic style and makes show shopping annoying and easy at the same time.
I think shoe sizes are extra bad for wide feet. When it comes to trying stuff on in a store I wear a 12 in most dress shoes, 14-15 in most running shoes. According to guy at the local shoe store I should be buying a 13 2E I think.
Yeah, there aren’t spinning disk m.2s coming. The whole focus of this GN was in the context of SSDs.
I guess AHCI has legacy mode (for IDE compatibility), regular mode (fine for spinning disks), and RAID mode (secret sauce). Using AHCI in any mode for SSDs is itself legacy.
There are PCIe cards that just have m.2 slots on them.
But for real, unless you’re looking for that sweet sweet NVMe performance, there’s no point. Regular old modern SSD with AHCI is still lightyears beyond a spinning disk.