AMD's 890GX Chipset in Gigabyte 890GPA-UD3H

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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.

Gigabyte Boards: 785G vs. 890GX
Test State
785GPMT-UD2H
890GPA-UD3H
System
CPU + VRM
Diff.
System
CPU + VRM
Diff.
Idle
34W
15W
19W
38W
12W
26W
Crash
(x264 22mbps)
 
53W
18W
35W
BD Disturbia
(H.264 33mbps)
62W
35W
27W
57W
18W
39W
BD Jane
(VC-1 36mbps)
63W
35W
28W
57W
18W
39W
CPU Load
108W
82W
26W
110W
79W
31W
CPU + GPU
Load
115W
83W
32W
128W
80W
48W

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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