The asynchronous port is a character-at-a-time device for both input and output. This characteristic both limits the bandwidth that can be achieved over a serial line, and increases the interrupt loading on the central processor. Applications like uucp(1bnu) and PPP may be able to function well at speeds greater than 9600 baud, depending on your system processor type and UART.
The serial port adapter's programmable baud rates do not correspond exactly with system baud rates. Specifically, setting B0 will cause a disconnect, setting EXTA will set 19200 baud, and setting EXTB will set 38400 baud. The asynchronous ports driver supports interrupt sharing, as well as line signal (hardware) flow control when the device node /dev/tty0?h is used. The /dev/tty0?s ports are software flow control nodes as are the /dev/tty0? nodes.
The asyc driver supports both 16450 and 16550 UARTs and equivalents.
The order of entries in the DCU and the corresponding entries in the asyc driver's space.c file must be in the same order for serial consoles to work correctly.
IRQ conflicts with an interrupt vector which cannot be shared...
,
you need to change the ``ITYPE'' field to 3;
apply the change, exit
dcu and reboot the system.