PCIe 6.0
The sixth generation of PCI Express (spec 2022). Doubles bandwidth to 64 GT/s per lane by switching signaling from NRZ to PAM4 (four voltage levels). A PCIe 6.0 x16 gives ~128 GB/s. Primarily for AI/datacenter hardware first.
Key change: PAM4 packs 2 bits per symbol (instead of NRZ's 1) → doubled rate without doubling frequency, but worse signal-to-noise → requires FEC (forward error correction) and a new FLIT-based framing. Driver: AI accelerators, high-speed NICs (800 GbE), CXL memory pooling that hunger for bandwidth. Backward compatible with earlier generations. PCIe 7.0 (spec 2025) already aims for 128 GT/s. Consumer hardware lags far behind — desktop was on 5.0 and started reaching 6.0 only in the server class in 2024-2025. Tightly linked to CXL development.