Hi g.f,
One way of reducing power consumption would be to power down the DSP whenever the idle task runs. This would typically involve programming certain power registers and then invoking the idle instruction in the idle task function. Please go through section 12.2.4 and section 12.2.5 from C66x CorePac's user guide (http://www.ti.com/lit/pdf/sprugw0) for more details on the steps required to power down the DSP core.
Best,
Ashish