If you've run out of serial ports on your computer, before you buy an ISA card to add more ports, check on things first: how many IRQ's (Interrupt Request Lines) do you still have free? If you're down to only one, better get a PCI card like this one. The reason is that a PCI 2.1 compliant card can allow multiple devices to share a single IRQ setting. Also, a PCI card reduces the load on your CPU, improving overall system performances.