Which side does the PCIe go In?

Solution
Just want to point out that modular connectors are keyed like 99%, and therefore will not fit in the incorrect socket. You only have to look at the shapes/pattern of the connector ends (squared, semi circular) to figure out what goes where.
Just want to point out that modular connectors are keyed like 99%, and therefore will not fit in the incorrect socket. You only have to look at the shapes/pattern of the connector ends (squared, semi circular) to figure out what goes where.
 
Solution