R4030_SYS_EXT_IMASK
out32(R4030_SYS_EXT_IMASK, cpu_int_mask);
out32(R4030_SYS_EXT_IMASK, cpu_int_mask & (~MIPS_INT_MASK_4 >> 10));
out32(R4030_SYS_EXT_IMASK, 0x00);