Packet drops / discards on interfaces

I'm looking for a way to read the packet drops on the interfaces of cisco switches.

There is an report-error info table job type, and it contains a lot of port variables.  But no packet drops or discards.

We have a Cisco 6500 chassis with 6148 48-port 10/100/1000  blades, but since these ports are 1:8 overbooked, we really need to monitor the packet drops to see what the impact of the overbooking is.

Thanks,

Joop