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Detailed DC Power Consumption
During testing we record power consumption both from the wall and from the
AUX12V connector with the help of a pair of digital multimeters and an in-line
0.1 ohm shunt resistor. The latter measures how much energy is being drawn on
the +12V line by the processor including inefficiencies lost to the VRMs. This
can help us narrow down the causes of power consumption differences between
two boards.
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Gigabyte Boards: 785G vs. 890GX
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Test State
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785GPMT-UD2H
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890GPA-UD3H
|
|
System
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CPU + VRM
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Diff.
|
System
|
CPU + VRM
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Diff.
|
|
Idle
|
34W
|
15W
|
19W
|
38W
|
12W
|
26W
|
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Crash
(x264 22mbps)
|
|
53W
|
18W
|
35W
|
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BD Disturbia
(H.264 33mbps)
|
62W
|
35W
|
27W
|
57W
|
18W
|
39W
|
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BD Jane
(VC-1 36mbps)
|
63W
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35W
|
28W
|
57W
|
18W
|
39W
|
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CPU Load
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108W
|
82W
|
26W
|
110W
|
79W
|
31W
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CPU + GPU
Load
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115W
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83W
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32W
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128W
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80W
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48W
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Our measurements from the AUX12V connector show that the board's CPU power
management is very good. The CPU and VRMs used 3W less at idle and on full load
compared to the Gigabyte 785G board we reviewed in December. During Blu-ray
playback the difference increased to an impressive 17W. Unfortunately, the overall
system power wasn't that different, indicating that the rest of the system was
actually using more power. The other portions of the motherboard and the remaining
components in our test system used 7W more when idle and 5W more when a full
CPU load was applied.
As we tested both mainboards using the same hardware, we have to conclude that
the 890GX motherboard is more power hungry. Sure, the compared 785G board is
mATX, but in our experience the form factor matters little when it comes to
of energy efficiency. Except for the chipset, the only major difference is the
included NEC USB 3.0 controller running on the PCI-E bus which could be the
culprit. When we reviewed the USB 3.0 enabled Asus P7H55D-M, we also found that
it used more power than expected.
As the HD 4290 IGP is more powerful than HD 4200, it used considerably more
power when stressed.
Video Playback
|
Gigabyte Boards: 785G vs. 890GX
|
|
Test State
|
785GPMT-UD2H
|
890GPA-UD3H
|
|
Avg.
CPU
|
Sys. Power (DC)
|
Avg.
CPU
|
Sys. Power (DC)
|
|
Rush Hour
(H.264 10mbps)
|
3%
|
56W
|
8%
|
47W
|
|
Coral Reef
(WMV 8mbps)
|
20%
|
61W
|
27%
|
57W
|
|
Crash
(x264 22mbps)
|
|
18%
|
53W
|
|
BD Disturbia
(H.264 33mbps)
|
7%
|
62W
|
17%
|
57W
|
|
BD Jane
(VC-1 36mbps)
|
7%
|
63W
|
21%
|
57W
|
The HD 3300 and HD 4290 graphics chips found on the 785G and 890GX boards respectively
both have the same version of ATI's UVD (Universal Video Decoder) and as such,
they both powered through our video playback test suite with little effort.
However, one would expect the CPU usage numbers to be similar, but in fact the
890GX board seemed to require more CPU cycles to render the same videos. We
found that the CPU utilization was higher because the processor was running
at lower frequencies and voltages during rendering. This explains the unusually
high CPU/VRM efficiency during video playback we mentioned earlier.
Undervolting
|
Estimated DC System Power Comparison
(X3 720 @ 1.6GHz, best undervolt, C&Q off)
|
|
Board
|
vCore
|
Idle
|
BD Disturbia
|
CPU Load
|
CPU + GPU
Load
|
|
MSI
785GM-E65
|
0.940V
|
31W
|
41W
|
45W
|
55W
|
|
Gigabyte
785GPMT-UD2H
|
0.950V
|
35W
|
44W
|
49W
|
58W
|
|
Asus
M4A78T-E
|
0.913V
|
35W
|
44W
|
46W
|
64W
|
|
Asus
M4A785TD-V
|
1.025V
|
43W
|
52W
|
57W
|
66W
|
|
Gigabyte 890GPA-UD3H
|
1.025V
|
37W
|
57W
|
62W
|
78W
|
We conducted our undervolting tests with the CPU running at 1.6GHz. The board
was Prime95 stable at 0.925V, but setting the voltage that low prevented the
system from POSTing on a cold boot. It would not startup with less than 1.025V
vCore. Compared to the Asus M4A785TD-V
running at the same voltage, the 890GPA-UD3H used 6W less when idle, but 5W
more during Blu-ray playback and on full CPU load, and an additional 12W when
the GPU was stressed as well due to the faster HD 4290 graphics core.
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