HelenOS sources
CLK_PORT4 97 kernel/arch/amd64/src/drivers/i8254.c pio_write_8(CLK_PORT4, 0x36);
CLK_PORT4 110 kernel/arch/amd64/src/drivers/i8254.c pio_write_8(CLK_PORT4, 0x30);
CLK_PORT4 120 kernel/arch/amd64/src/drivers/i8254.c pio_write_8(CLK_PORT4, 0xc2);
CLK_PORT4 128 kernel/arch/amd64/src/drivers/i8254.c pio_write_8(CLK_PORT4, 0xd2);
CLK_PORT4 135 kernel/arch/amd64/src/drivers/i8254.c pio_write_8(CLK_PORT4, 0xd2);
CLK_PORT4 141 kernel/arch/amd64/src/drivers/i8254.c pio_write_8(CLK_PORT4, 0xd2);
CLK_PORT4 97 kernel/arch/ia32/src/drivers/i8254.c pio_write_8(CLK_PORT4, 0x36);
CLK_PORT4 110 kernel/arch/ia32/src/drivers/i8254.c pio_write_8(CLK_PORT4, 0x30);
CLK_PORT4 120 kernel/arch/ia32/src/drivers/i8254.c pio_write_8(CLK_PORT4, 0xc2);
CLK_PORT4 128 kernel/arch/ia32/src/drivers/i8254.c pio_write_8(CLK_PORT4, 0xd2);
CLK_PORT4 135 kernel/arch/ia32/src/drivers/i8254.c pio_write_8(CLK_PORT4, 0xd2);
CLK_PORT4 141 kernel/arch/ia32/src/drivers/i8254.c pio_write_8(CLK_PORT4, 0xd2);
HelenOS homepage, sources at GitHub