If it doesn't work at all, then you need to make sure your serial port can be found. Check the BIOS menus and BIOS messages. For the PCI bus use lspci. You may try probing with setserial. See Probing If nothing seems to get thru the port it may be there but have a bad interrupt.
Text appears on the screen slowly after long delays .
Here are some of the symptoms which will happen the first time you try to use a modem, terminal, or printer. In some cases you type something but nothing appears on the screen until many seconds later. Only the last character typed may show up. In other cases where a lot of data should appear on the screen, only a batch of about 16 characters appear. Then there is a long wait of many seconds for the next batch of characters.