How to know that M.2 SSD PCIe 4.0 disk is backward compatible with PCIe 3.0 / 2.0 PCI expansion bus? I want to connect PCIe 4.0 disk through adapter.

Thank you!

1 Answer 1


As far as I know, all PCIe versions are both backwards and forwards compatible (don't know about PCIe 6, but no hardware with that yet). With compatibility for now, just check you are really using PCIe and not PCI (thats incompatible).

  • People told me that "Some SSDs PCIe 4.0 doesn't work with PCIe 3.0 through the adapter" is it untrue?? People said "PCI Express 3.0 x16 has speed 15.8 Gigabyte/second and some PCIe 4.0 SSDs can achieve 7500 Mbyte/second performance through the adapter, but other SSDs doesn't work at all" May 9 at 18:49
  • SSD's don't have x16 PCIe, but only x4. So that means that PCIe 4.0 SSD will be bottlenecked by the slot, not the adapter (since it's passive), to 4GBps (which is still too fast). Since all PCIe revisions until now are backwards compatible, this also counts with SSDs.
    – Irsu85
    May 10 at 6:17
  • Do you mean that bundle M.2 SSD PCIe 4.0 x 4 <=> PCIe 3.0 x 16 adapter <=> PCIe 3.0 x 16 motherboard slot will be forced to PCIe 3.0 x 4 speed? People told me different, they said such bundle will be forced to PCIe 3.0 x 16 speed which is very fast. May 10 at 8:21
  • Yes, AFAIK that is the case with normal adapters. Maybe there are active adapters where it will be bolltlenecked by PCIe4.0 x4, but I don't know
    – Irsu85
    May 10 at 8:55

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