You want it set as SSO mode. If its standby cold then it's either  not setup as SSO  or the supervisors do not have the exact same code on it.Standby cold will not failover nearly as fast as if it was hot.

Hi,

In Catalyst 6500 Series Switches allow a redundant Supervisor Engine to take over if the primary Supervisor Engine fails in order to support fault resistance. Redundant Supervisor Engines must be of the same type with the same model feature card to support redundancy. When you install two Supervisor Engines, the first one to come online becomes the active module. The second Supervisor Engine goes into standby mode.

Redundant Supervisor Engines are hot swappable. The system continues to operate with the same configuration after it switches over to the redundant Supervisor Engine.

Redundancy is always enabled and cannot be disabled. Redundancy is enabled anytime the switch has two Supervisor Engines installed on it and the switch decides which specific redundancy mode to use in accordance to the type of images it has.

Check out the below link hope this clears your query !!

http://www.cisco.com/en/US/products/hw/switches/ps708/products_configuration_example09186a0080a98f3c.shtml

Regards

Ganesh.H