Ordinarily a chip installed on a board like the serial port chip of a standard manufacturer will die due to "normal" static. What kills a serial port chip of a PC is mains leakage. In more detail: the SMPS of a PC as with any other well designed equipment for safety reasons, has the ground of +5V connected to the earth of the incoming mains supply. Now if the equipment you connect to the serial port is not grounded then the leakage of its PSU will discharge through the serial port of the PC and this kills the port chip. Very common with the most of the laptops that we get here, which have unearthed 2 pin supplies. So check with a line(leakage) tester the instruments before connecting to each other.