by tnt » Sat Jul 05, 2014 10:52 pm
The Altera equivalent you posted is ... well equivalent, it won't have an especially better / worse power/speed ratio. The microsemi link is a ridiculously slow CPU implementation, probably 50x slower at least that the one in the Zynq.
You're right that the CPU in mobile phones are remarkably low power. Certainly a lot more than que Zynq ES we have, but a lot of this is also due to aggressive power management (shutting down or slowing down unused parts) and dedicated hw accelerators for the common tasks (like video playing which use very little the CPU).
But as stated above, you'll need a separate FPGA anyway for the epiphany interfacing which will eat your power gain of having a separate CPU, reduce the bandwidth between CPU and epiphany (and the external memory) and eat more board real-estate. So that doesn't seem like a viable idea.
As for the datasheet you can google for DS187, it will give you a lot of the numbers for the static consumption. But for the dynamic one, you need to go through the xilinx tools because, being heavily programmable, the FPGA power usage can vary dramatically depending on the way it's used.
But all in all, it's not that relevant. We know the whole board consumes 5W. Those 5W end up purely in heat and must be dissipated to the ambient air somehow and with such a small surface and a lot of it covered by component, it's definitely a challenge. For comparaison, a RPi is about 2.5W (and it's definitely more than twice slower !), so the energy efficiency of the board, even with the ES is really not bad, it just needs to reduce the theta-ja of the system to achieve passive cooling.