After upgrading to BOINC 7.0.28, I noticed the same situation when pauzed/restarted after a change in cmd-line settings, running High Priority inmediatly after this. This also happens when doing a few hundred MW WUs, taking about an hour.Don't know if anyone noticed this too, but it looks like the very same behavior as BOINC7.0.25 !Not only on my ATI rig, also on 2 CUDA rigs.
Whatever your issue may be, it has nothing to do with the subject of this thread.As of two minutes ago, dont_use_dcf was still not active at SETI main.
Oh, and the rumor I heard about the downclock was that it was caused by the 301 driver and related to card temperature. It apparently triggers the downclock at too low a temperature. After a reboot to reset it it runs fine untill the next event.