The design guide shows the Insertion loss budget at 20dB, but the PCIe 4.0 spec is 28 dB. So, if I need to meet the PCIe 4.0 loss budget, do I need a retimer to realize the PCIe loss spec?
I want to extend the orin PCIE 4. 0 8x to a PCIE 4.0 8x device by long PCB routing with pcie 4.0 connector. I want to calculate the PCB trace loss budget.
Refer to the PCIe CEM specification for the link budget allocation. Design Guide provides the insertion loss budget for the PCB traces portion only and for different use cases like direct to device or second Orin module and NVMe connector/card.
Refer to Note below for the assumptions.
sgursal,
for the direct-to-device case. it means the max PCB loss is 20.51dB with EM-370 PCB material，
if I plug the orin module on the backplane using PCIE 4.0 connector, and connect to another pcie4 connector with IB pcie4.0 8x IB card,but the two pcie4.0 connector’s distance is about 40cm, even I use ultra low loss, it is still out of the orin loss budget, so I need a retimer, which can increase the loss budget do 38dB, so I can make whole PCB link working at pcie 4.0 speed within the long distance。
So please help by suggesting adding a retimer. Can the long-distance PCIe 4.0 link work?
If I need the retimer, is there any guide on how to implement it? Or is it enough to follow the design guide from the retimer supplier?
We do not have recommendation for PCIe retimer. Suggest to check with PCIe retimer vendors and follow their recommended guidelines to meet your intended use case.