- The clock issue has nothing to do with single / crossfire setups.
- The way described in the videos doesn't work for newer revisions of either cards or drivers.
- AMD Overdrive does not OC the card at all times. It still clocks down and just goes up higher under full load
- You can use a simple tool called "System Monitor" from AMD to check if your card is going to it's maximum clock or not. It shows everything nicely. It's most likely already installed on your machine. Just press the windows key and type: "system monitor" and wait a couple of seconds. Or you can just download it
here