The I/O chassis secures the PCI Express ExpressModules (EMs; Sun Blade 8000 Chassis only), the Network Express Modules (NEMs), and the Chassis Monitoring Modules (CMMs) within the chassis. The I/O chassis includes the midplane, AC inlets, and main cable harness. The I/O chassis is a field-replaceable unit (FRU); only authorized service personnel can service this component. Typically, you will only need to remove and replace the I/O chassis if there is a problem with the midplane. The system must be powered off before you can service the I/O chassis.