"PCIe 4.0 May Be Short-Lived. PCIe 5.0 Is Almost Here"...
What We Know About PCIe 4.0 So Far
by Lucian Armasu April 14, 2019 at 6:00 AM
PCIe 4.0 May Be Short-Lived. PCIe 5.0 Is Almost Here
Because the PCIe 4.0 specification was finalized a few years late, we ended up with a situation where the PCIe 5.0 specification was finalized only a couple of years later.
The PCI-SIG group recently published the 0.9 version of the PCIe 5.0 specification, and we should see support for it in computing products as soon as next year. As usual, the PCIe 5.0 generation will double the bandwidth of PCIe 4.0 to 32GT/s or ~8GB/s per lane (bi-directional), for a total of 128GB/s for 16 lanes.
PCIe 4.0 Performance
Credit: PCI-SIG
PCIe slots can be configured with one lane or multiples of four lanes, such as x1, x4, x8, x16, x32. Each new generation doubles the bandwidth of the previous one. For instance, a PCIe 3.0 x8 interface can be replaced by a PCIe 4.0 x4 interface that provides the same amount of bandwidth.
| Bandwidth
| Gigatransfer
| Frequency
| Encoding
| PCIe 1.0
| 8 GB/s
| 2.5 GT/s
| 2.5 GHz
| 8b/10b
| PCIe 2.0
| 16 GB/s
| 5 GT/s
| 5.0 GHz
| 8b/10b
| PCIe 3.0
| 32 GB/s
| 8 GT/s
| 8.0 GHz
| 128b/130b
| PCIe 4.0
| 64 GB/s
| 16 GT/s
| 16.0 GHz
| 128b/130b | PCIe 5.0
| 128 GB/s
| 32 GT/s
| 32.0 GHz
| 128b/130b |
The PCIe 4.0 standard supports a 16 GT/s bit rate, (roughly 2GB/s per single lane, or 64GB/s in total) as opposed to 8GT/s bit rate for PCIe 3.0 (1GB/s).
The PCIe standard maintains both backward and forward compatibility with older and newer specifications via both software and mechanical interface. In other words, PCIe 3.0 cards will work on motherboards that support PCIe 4.0, and PCIe 4.0 cards will also work on PCIe 3.0 motherboards, but they are limited to the performance of the PCIe 3.0 interface.
The PCIe 4.0 specification will also bring the OCuLink-2 connector, an alternative to Thunderbolt 3, that provides 8GB/s of bandwidth via four PCIe 4.0 lanes. In comparison, the Thunderbolt 3 connector provides up to 5GB/s of bandwidth. |
