serial port does not work on PC104

Hi Everyone,
I am now using a PC104 (model: nano-4386A, vendor IEI world),
which will be running linux.

Now I installed fedora core 6(kernel 2.6). but COM1 does not work
all. I have installed winXP on the same hardware platform, COM1 works
well. So the hardware is OK. Here is detailed info.

(1) hardware configuration: NANO-4386A, Pentium 1.6GHz, Sandisk 8GB CF
card, 1GB Ram, no hard disk. Keep the jumpers on the board as default
(2) Loop back connect the COM1, that is connecting TXT to RXD. It is a
9 pin port. send and receive through the same port.
(3) Install linux OS(fedora core 2.6, kernel 2.6) on it.
(4) Test using sct, a software tool for serial port debugging.
(5) NO output through COM1, cannot receive either.
(6) The same program sct works well on my desktop, which installed the
same OS using the same DVD disk.
By the way, there is 6 serial ports on the board.Even if I disable
the other 5 in BIOS, the only /dev/ttyS0 does not work.
(7) I can see the io address and IRQ number is correct by "dmesg |
more tty*"
Is there anything I should pay attention to?
Thank you!