It seems that the kernel (2.6.10) isn't properly initializing the Au1550 serial ports. All three of the serial ports work, just not at the same time. Linux seems to need yamon to configure the serial port first. Out of the box yamon uses UART0 & UART3 and ttyS0 & ttyS2 (UART3, the 1550 doesn't have a UART2) work in linux, but ttyS1 doesn't. If I switch yamon to use UART1 & UART3, then ttyS0 doesn't seem to work in linux. The serial port that isn't configured by yamon will hang in an ioctl() on calling tcsetattr(). Before I just cheat and add a third serial port to yamon, should the kernel be initializing the UARTs or does it really expect the yamon to initialize them first? Is anyone using all 3 serial ports on an Au1550? Thanks, Clem