Yamaha CRW8424SX Series Owner's Manual page 27

Setting Up The CRW8424SX Drive
4 Power up your CRW8424SX drive first, then your computer.
Always power up the devices in your SCSI chain before powering up
your computer. This will ensure that they are recognized by the
computer's operating system.
Do not disconnect any devices in your SCSI chain while the computer is on.