OK, a PCIe has one or more lanes. Each lane is made up of two transmit wires and two receive wires.
PCIe is a serial connection so it sends and receives one bit at a time. Why are there two wires for one bit? How does that work?
Signal and ground? In general, when you send a signal along a wire, there has to be something to relate it to, in order to receive it as a signal at the other end. (There are exceptions to this, and not all technologies choose to have a separate ground for each signal line.
:smack: Oh duh, I should I have thought of that. Anyway, thank you.
I should add that I don’t know this to be a fact for this technology, but it seems highly likely - and having a separate ground for each serial signal probably keeps things clean and isolated, allowing a faster bit rate.
Not signal and ground, but Differential Signaling. While the voltage on one line swings positive, the voltage on the other line swings negative (about a “common-mode” voltage level defined by the interface protocol). This has much better noise-rejection performance than would happen if one line were tied to a local ground.
The same technique is used in longer-distance serial buses sch as USB, Firewire, and SATA (all flavors of each).
OK, now that I never would have thought of. Thank you for the answer and the link.
I didn’t read the link provided by Antonius Block, so this may be redundant:
Differential signalling is also useful when communicating between two pieces of equipment that have a different idea of what “ground” is. It’s also used for MIL-STD-1553 serial communications for that reason.