I had this problem with uboot too. Add the line at91_pio_use_periph_a(AT91RM92_PIOA_BASE, AT91C_PA27_MCCK | AT91C_PA28_MCCDA | AT91C_PA29_MCDA0, 0); to the function board_init() in kb920x_machdep.c and try again. Regards Björn