bandwidth v/s clock rate.

"Clock Rate" is the physical rate, at which data are transmitted. It's your actual speed.

"Bandwidth" command has nothing to do with your physical speed. This is a parameter used by some routing protocol to calculate a routing metric.

For example, you may have 10MBit interface and 100MBit interface going to the same location. By default 10MBit interface will have the bandwidth 10000, and 100 MBit - 100000 accordingly, and your 100 MBit interface will be prefered over the 10 MBit. Now, if you change the bandwidth parameter (bandwidth command at the interface level) for the
100 MBit interface to 1000 (one thousand), even though your physical speed is not changed, your router will think that 10 MBit interface is better route and will use it.

Good luck,

Mike
CCNP, CCDP, CCSP, Cisco Voice, Security+, etc.
----
http://www.ciscoheadsetadapter.com

As part of the answer "clockrate" is used in two scenarios, a lab environment and a live environment. The clockrate in a live environment is set on the WAN p2p link from your service providor (DCE)(Wall-Connector). In a lab environment you may have two routers connected together for testing by a WAN link cable but one of the WAN interfaces (DCE)must have a clockrate set to dupe the other (DTE) into thinking it is connected to a service providor connection (DCE). As mentioned earlier by Mike, bandwidth is used in part of the algorithm to calculate the metric of the link.

Many sources on the internet to find an answer for that problem. I'm not an expert in ds3 connections but you may get an answer at http://en.wikipedia.org/wiki/Cisco_Systems