EMC Connectrix B Series Hardware Reference Manual page 25

Overview
WARNING
Upgrade firmware on the ED-48000B to the level required for any
new blades before you install the new blades (v5.1.0 or greater for the
PB-48K-18i, v5.2.0 or greater for the PB-48K-48). Do not install a
blade into a director running an unsupported version of Fabric OS for
that blade.
Note: The PB-48K-18i blade powers up in a persistently disabled state until
the ports are persistently enabled. This allows you to configure new ports
before enabling them in the system.
After the POST is complete, the firmware version on the PB-48K-18i blade
will autolevel with the firmware version on the active CP. You must have
Fabric OS v5.1.0 or higher or the PB-48K-18i blade will be faulted. For more
information see the EMC Connectrix B Series PB-48000B-18i Hardware Reference
Manual.
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PB-48K-18i blade