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Table V gives the energy breakdown by
hardware for the systems targeted when they are idle and while
performing the aforementioned DCT computation. It also gives the
one-second energy consumption in EU for different components. The
LCD energy is obtained by comparing the system energy before and
after the LCD is turned off. Front-light energy is obtained in the
same way. ``Others" refers to the system energy minus the LCD and
front-light energy. It includes the energy consumed by all other
hardware. The table shows that the front light and the TFT LCD
consume a large fraction of system energy. The percentages are
larger than those reported for notebook
computers [4], in which a hard-disk,
system-on-board and more powerful processor are used instead of
Flash memory and SOCs.
Table V:
System energy breakdown for the handheld computers
Handheld |
LCD |
Front light |
Others |
EU |
|
% |
EU |
% |
EU |
% |
EU |
Joule |
iPAQ1 |
idle |
9 |
18,800 |
73 |
147,100 |
18 |
35,300 |
8.0 |
|
DCT |
7 |
|
53 |
|
40 |
112,600 |
|
iPAQ2 |
idle |
14 |
20,600
|
53 |
77,700 |
33 |
48,200 |
9.8 |
|
DCT |
9 |
|
34 |
|
57 |
129,100 |
|
Zaurus |
idle |
11
|
25,200 |
80 |
180,000 |
9 |
19,000 |
9.3 |
|
DCT |
8 |
|
59 |
|
33 |
99,300 |
|
With the front light turned off, the TFT LCD consumes from 14% to
55% of the system energy, depending on how busy the CPU is.
However, it should be noted that in interactive application usage,
the CPU is idle most of the time.
Next: Event handling and basic
Up: GUI energy characterization
Previous: GUI energy characterization
Lin Zhong
2003-10-13