Not every "M.2 slot" on a Z790 or X670E motherboard actually supports PCIe 5.0. The spec requires enhanced PCB routing and separate clock buffers. Look for mentions of "PCIe 5.0 M.2" and "low-loss PCB" in your board's manual—those are cues that the manufacturer adhered to Rev 5.0.
You're looking for information on the PCI Express M.2 specification, specifically revision 5.0, version 1.0. Here's what I found: pci express m.2 specification revision 5.0 version 1.0 pdf
Before diving into Revision 5.0, it is essential to understand the document itself. The M.2 specification is not managed by the PCI-SIG alone; it is a joint effort, often stored under the auspices of organizations like JEDEC and the PCI-SIG working groups. Not every "M
