zlacker

1x PCIE 3.0 has 8 Gbps raw speed - for 2.5Gbps duplex Ethernet you'll need 6~7 Gbps of raw link to CPU.

For 5Gbps and higher, you'll need another PCIE line - and SOHO motherboards are usually already pretty tight on PCIE lanes.

10GbE will require 4x3.0 lanes

>>u8080+(OP)
Are motherboards commonly using PCIe 3.0 for onboard peripherals these days? I wouldn’t expect it to save them much money, but my PCIe knowledge is constrained to the application layer - I know next to nothing about the PHY or associated costs.

>>u8080+(OP)
This is got to be it!

>>u8080+(OP)
PCIe is full duplex. And there's no requirement for ethernet ports to be able to do full tilt. Even with a 1x PCIe 3.0, a 10G port will be much much better than a 2.5G one.

(But PCIe 3.0 of course is from 2010 and isn't too relevant today - 4.0, 5.0, 6.0 and 7.0 have 16/32/64/128 Gbps per lane respectively)

>>u8080+(OP)
> 10GbE will require 4x3.0 lanes

3.0 PCIE is irrelevant today when it comes to devices you want on 10G. I'm pretty sure the real reason is that 2.5G can comfortably run on cable you used for 1G[1], while 10G get silly hot or requires transceiver and user understanding of a hundred 2-3 letter acronyms.

Combine it with IPS speeds lagging behind. 2.5G while feels odd to some, makes total sense on consumer market.

[1]: at short distances, I had replaced one run with shielded cable to get 2.5G, but it had POE, so it might contribute to noise?)