Yokemate of Keyboards
Posts: 11609 from 2003/5/22
> The P1022 on the Tabor/A1222 riddles me. [...] PCIe x4 + 2x SATA + GbE would
> obviously require 7 SerDes lanes. Something seems not right here. Any ideas?
Mystery solved, and the solution is foreheadslappingly easy: Just as with the newer T1022/T1042, the P1022 does not require any SerDes lanes for the GbE controller if in RGMII mode.
What had me confused was the simplified P1022 block diagram
which implies that the GbE controllers would only work with SerDes lanes assigned to them. Looking at a more detailed P1022 block diagram
reveals that the SerDes lanes of the P1022 are assignable to SGMII-mode GbE, but not to RGMII-mode GbE (which is what is used on A1222/Tabor).
The block diagrams of the P1022RDK board
and the P1022DS board
also illustrate this.
So in conclusion, the 6 SerDes lanes of the P1022 supply the PCIe slot with 4 lanes and the two SATA2 ports with 1 lane each, and GbE is provided by the eTSEC/VeTSEC in RGMII mode.