Okay, I tried tweaking the cgminer.sh script to setup my board with a PLL setting of 0x01,0x68.  Power consumption did not change.  I also tried 0x00,0x68; again no change.  This was tested with a restart of the service.  I haven't tried a reboot (would need to modify the BBB's flash or something).  It's possible the PLL settings can be set only once per power-cycle, but that'd be a bit out of the ordinary.