ECE471: Embedded Systems – Homework 10
Power/Performance
Power and Energy
Table 1: OpenBLAS HPL N=10000 (Matrix Multiply)
Machine Processor Cores Frequency Idle Power Load Power Time Total Energy
Raspberry Pi 2 Cortex-A7 4 900MHz 1.8W 3.4W 454s 1543J
Dragonboard Cortex-A53 4 1.2GHz 2.4W 4.7W 241s 1133J
Raspberry Pi 3 Cortex-A53 4 1.2GHz 1.8W 4.3W 178s 765J
Jetson-TX1 Cortex-A57 4 1.9GHz 2.1W 13.4W 47s 629J
Macbook Air Broadwell 2 1.6GHz 10.0W 29.1W 14s 407J
1. Table 1 shows the energy use of various machines when doing a large Matrix-Matrix multiply.
(a) Which machine has the lowest under-load power draw?
(b) Which machine consumes the least amount of energy?
(c) Which machine computes the result fastest?
2. Consider a use case with an embedded board taking a picture once every 60 seconds and then performing a matrix-multiply similar to the one in the benchmark (perhaps for image-recognition purposes).
Could all of the boards listed meet this deadline?
3. Assume a workload where a device takes a picture once a minute then does a large matrix multiply (as
seen in Table 1). The device is idle when not multiplying, but under full load when it is.
(a) Over an hour, what is the total energy usage of the Jetson TX-1?
(b) Over an hour, what is the total energy usage of the Macbook Air?
4. Given your answer in the previous question, which device would you choose if you were running this
project off of a battery?
Submitting the Assignment
Please put your answers to questions 1 - 4 in some sort of document (text, pdf, doc) and *e-mail* it to me
by the deadline.
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