Is it the SerDes component that also does the word encoding (8b10, etc., forgot the proper terminology for this) ?
I work on the Hardware/Software interface quite a bit (more in the past than now) and this is always fascinating, I'm on the Software side, thanks for the details!
The encoding takes 8 bits and turns them into 10 for DC balance and to help the clock recovery system. You are basically losing 20% of your bandwidth to encoding overhead.
PCIE Gen 3 and above have switched to 64b/66b encoding for less overhead.
I work on the Hardware/Software interface quite a bit (more in the past than now) and this is always fascinating, I'm on the Software side, thanks for the details!