This is a quote from your link
While overclocking the HD 6990 we set the switch to the position 1 "AUSUM" setting to make use of the additional power. At this setting we were able to push the Cayman GPUs upward of 1000MHz, which was well beyond our exceptions.
so they didn't just flip the switch
This marginally concerns me... The 1000MHz OC is irrelevant as long as they did not increase voltage beyond those set by the swich change. Increasing clock speed can make the card to "crash" ie yield invalid results, fail CRC checks, the internal ones to the cpu/gpu etc, but pumping up Hz without increasing voltage can not burn up the card, cpu or what ever else...