PCIe 4.0 vs PCIe 5.0 vs PCIe 6.0
PCIe 4.0 runs 16 GT/s per lane. PCIe 5.0 doubles that to 32 GT/s. PCIe 6.0 doubles it again to 64 GT/s with PAM4 signaling.
PCIe 4.0, PCIe 5.0 and PCIe 6.0 are successive generations of PCI Express, the serial link between a CPU and its GPUs, network adapters and drives. Each doubles the per-lane rate of the last, measured in gigatransfers per second (GT/s): 16 GT/s, 32 GT/s and 64 GT/s. Every generation is backward compatible, so cards and slots of different generations work together.
PCIe 4.0 and PCIe 5.0 use 128b/130b encoding. PCIe 6.0 switches to four-level pulse amplitude modulation (PAM4), which carries two bits per symbol. It moves data in 256-byte flow control units, or flits, protected by forward error correction. A x16 link carries a raw 32 GB/s per direction at 16 GT/s, 64 GB/s at 32 GT/s and 128 GB/s at 64 GT/s. On select Grace Blackwell platforms, NVIDIA's ConnectX-8 network adapters and Blackwell GPUs run PCIe 6.0 x16 for up to 800 Gb/s of networking. The Grace CPU supports only PCIe 5.0, which caps an adapter behind it at 400 Gb/s.
Specify PCIe 6.0 only when both ends of a link support it, such as a ConnectX-8 adapter wired straight to a Blackwell GPU. Check the CPU first, since a PCIe 6.0 device behind a PCIe 5.0 CPU runs at PCIe 5.0 speed.
Sources
Source | Publisher |
|---|---|
Intel | |
An Introduction to the Compute Express Link (CXL) Interconnect | arXiv |
Enabling Fast Inference and Resilient Training with NCCL 2.27 | NVIDIA |
- Publisher
Intel
Last verified October 7, 2026.
- PCIe 4.0 vs 5.0
- PCIe 5.0 vs 6.0
- PCIe Gen5 vs Gen6
- PCIe 6.0 meaning
- PAM4 vs NRZ
- PCIe flit mode
- GT/s per lane
- PCIe x16 bandwidth
- PCIe backward compatibility
- ConnectX-8 PCIe Gen6