Check the BIOS menus and BIOS messages. For the PCI bus use lspci or scanpci. You may try probing with setserial. See Probing . If nothing seems to get thru the port it may be accessible but have a bad interrupt.
Text appears on the screen slowly after long delays .
Use setserial -g to see what the serial driver thinks and check for IRQ and I0 address conflicts. If two ports have the same IO address then probing it will erroneously indicate only one port. See Probing . Here are some of the symptoms which will happen the first time you try to use a modem, terminal, or serial printer. In some cases you type something but nothing appears on the screen until many seconds later.