I'm (still) putting an old Pentium PC together. I just found that the connectors of my serial port's ribbon cable have one less hole than needed. The socket on the mainboard has 10 pins, but the 10th hole of the connector is blocked. I have two serial ports, and both have the same connector.
The parallel port's connector is good. Later I found that the IDE cables also had a blocked hole. Fortunately I had a pair of "regular" ones, so that's not an issue. But I don't remember ever seeing connectors like this in the IDE era.
Can I simply drill the missing hole into the connector so it sits in the socket? To the best of my knowledge, a serial port has 9 pins, not 10.
Does the 10th pin do anything?