The C1 controller appears to be based on the Beaglebone Black (BBB) open source design which has a 1Ghz Sitara.. this should make the web interface of the C1 much more responsive than what is experienced with the S3 miner.
This picture shows a fully populated BBB, it's safe to assume the included BBB will be a board stripped down to the essential components to run the C1 miner.. however, if your board ever failed it would be easy to replace with a BBB.


The S2 used this stripped down BBB as well. I believe a number of S2 owners replaced that controller with a "full" BBB.