Computation Energy Randy Huang Sep 29, 1998
Dec 22, 2015
Outline
Why do we care about energy/power Components of power consumption Measurements of power consumption Reduction of power consumption Summary
Introduction
What is computation energy? Why do we care about energy?
– PGAs excel in multi-media applications that are needed in hand-held battery-operated devices
– easy to build devices that burn hundreds of watts if not careful
Energy and Power
Energy = Power / Toggle Frequency Pavg = Pdyn + Psc + Pleak + Pstatic
Pdyn is about 90% of power consumption
Dynamic Power Consumption
P = C x Vdd x Vswing x f x activity factor Look at graph of inverter Look at typical values
Power Measurement
Get a real chip and measure it Get a circuit design and simulate it Build a model
Question: why would you choose one method over another?
Xilinx 4003 Measurements
Look at table of Xilinx measurements Compared to the typical value we
calculated earlier
Why is interconnect so bad?
Look at a picture of heavily loaded FPGA interconnect with series connection of switches explain series of resistance effect plus transistor hanging off the interconnect, that it becomes highly resistive and capacitive
Build a model
Cautionary words from Randy Power factor approximation method
from UC San Diego Dual bit type model from UC Berkeley
Power Consumption Reduction
Review dynamic power consumption Hierarchy of low power technique
– algorithm– architecture– logic/cad– circuit– device
Architecture Level Technique
Pipelining Gated clock Reducing the number of busses and
switches Reducing fanout? Size of CLB