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TEST RESULTS
For a fuller understanding of ATX power supplies, please read the reference
article Power Supply Fundamentals & Recommended
Units. Those who seek source materials can find Intel's various PSU
design guides at Form
Factors.
For a complete rundown of testing equipment and procedures, please refer to
SPCR's PSU Test Platform
V.3. The testing system is a close simulation of a moderate airflow
mid-tower PC optimized for low noise.
In the test rig, the ambient temperature of the PSU varies proportionately
with its output load, which is exactly the way it is in a real PC environment.
But there is the added benefit of a high power load tester which allows incremental
load testing all the way to full power for any non-industrial PC power supply.
Both fan noise and voltage are measured at various standard loads. It is, in
general, a very demanding test, as the operating ambient temperature of the
PSU often reaches >40°C at full power. This is impossible to achieve
with an open test bench setup.
Great effort has been made to devise as realistic an operating
environment for the PSU as possible, but the thermal and noise results obtained
here still cannot be considered absolute. There are too many variables in PCs
and too many possible combinations of components for any single test environment
to provide infallible results. And there is always the bugaboo of sample variance.
These results are akin to a resume, a few detailed photographs, and some short
sound bites of someone you've never met. You'll probably get a pretty good overall
representation, but it is not quite the same as an extended meeting in person.
REAL SYSTEM POWER NEEDS: While our testing loads the PSU to full output
(even >600W!) in order to verify the manufacturer's claims, real desktop
PCs simply do not require anywhere near this level of power. The most pertinent
range of DC output power is between about 65W and 250W, because it is the power
range where most systems will be working most of the time. To illustrate this
point, we conducted system tests
to measure the maximum power draw that an actual system can draw
under worst-case conditions. Our most powerful Intel 670 (P4-3.8) processor
rig with nVidia 6800GT video card drew ~214W DC from the power supply under
full load ? well within the capabilities of any modern power supply. Please
follow the link provided above to see the details. It is true that very elaborate
systems with SLI could draw as much as another 100W, perhaps more, but the total
still remains well under 400W in extrapolations of our real world measurements.
SPCR's high fidelity sound
recording system was used to create MP3 sound files of this PSU. As
with the setup for recording fans, the position of the mic was 3" from the exhaust
vent at a 45° angle, outside the airflow turbulence area. The photo below shows
the setup (a different PSU is being recorded). All other noise sources in the
room were turned off while making the sound recordings.
INTERPRETING TEMPERATURE DATA
It important to keep in mind that fan speed varies with temperature,
not output load. A power supply generates more heat as output increases, but
is not the only the only factor that affects fan speed. Ambient temperature
and case airflow have almost as much effect. Our test rig represents a challenging
thermal situation for a power supply: A large portion of the heat generated
inside the case must be exhausted through the power supply, which causes a corresponding
increase in fan speed.
When examining thermal data, the most important indicator of cooling efficiency
is the difference between intake and exhaust. Because the heat
generated in the PSU loader by the output of the PSU is always the same for
a given power level, the intake temperature should be roughly the same between
different tests. The only external variable is the ambient room temperature.
The temperature of the exhaust air from the PSU is affected by several factors:
- Intake temperature (determined by ambient temperature and power output level)
- Efficiency of the PSU (how much heat it generates while producing the required
output)
- The effectiveness of the PSU's cooling system, which is comprised of:
- Overall mechanical and airflow design
- Size, shape and overall surface area of heatsinks
- Fan(s) and fan speed control circuit
The thermal rise in the power supply is really the only indicator
we have about all of the above. This is why the intake temperature is important:
It represents the ambient temperature around the power supply itself. Subtracting
the intake temperature from the exhaust temperature gives a reasonable gauge
of the effectiveness of the power supply's cooling system. This is the only
temperature number that is comparable between different reviews, as it is unaffected
by the ambient temperature.
On to the test results...
Ambient conditions during testing were 20°C and 20 dBA, 121W/60Hz.
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OUTPUT & EFFICIENCY: Zalman ZM460-APS
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|
DC Output Voltage (V) + Current (A)
|
Total DC Output
|
AC Input
|
Calculated Efficiency
|
|
+12V1
|
+12V2
|
+5V
|
+3.3V
|
-12V
|
+5VSB
|
|
12.24
|
0.97
|
12.22
|
1.74
|
5.10
|
0.99
|
3.34
|
0.00
|
0.1
|
0.2
|
40.4
|
62.1
|
65.0%
|
|
12.25
|
1.92
|
12.23
|
1.74
|
5.09
|
1.96
|
3.33
|
1.86
|
0.1
|
0.3
|
63.7
|
89.1
|
71.5%
|
|
12.23
|
1.91
|
12.20
|
3.32
|
5.08
|
2.91
|
3.3
|
2.75
|
0.2
|
0.4
|
92.2
|
122.2
|
75.5%
|
|
12.21
|
4.80
|
12.20
|
3.32
|
5.05
|
5.66
|
3.31
|
4.55
|
0.3
|
0.7
|
149.9
|
190.4
|
78.7%
|
|
12.19
|
5.74
|
12.16
|
5.01
|
5.03
|
7.28
|
3.31
|
7.51
|
0.4
|
0.9
|
201.7
|
249
|
81.0%
|
|
12.16
|
7.82
|
12.12
|
6.47
|
5.01
|
8.17
|
3.30
|
7.49
|
0.4
|
1.1
|
249.5
|
308
|
81.0%
|
|
12.13
|
8.76
|
12.08
|
8.12
|
4.99
|
10.70
|
3.28
|
9.13
|
0.5
|
1.3
|
300.2
|
373
|
80.5%
|
|
12.14
|
10.59
|
12.04
|
11.23
|
4.94
|
14.61
|
3.26
|
14.05
|
0.7
|
1.7
|
398.6
|
508
|
78.5%
|
|
12.08
|
13.31
|
12.00
|
12.60
|
4.92
|
16.19
|
3.25
|
15.53
|
0.8
|
2.0
|
461.7
|
599
|
77.1%
|
|
NOTE: The current and voltage for -12V and +5VSB
lines is not measured but based on switch settings of the DBS-2100 PS
Loader. It is a tiny portion of the total, and potential errors arising
from inaccuracies on these lines is <1W.
|
|
OTHER DATA SUMMARY: Zalman ZM460-APS
|
|
DC Output (W)
|
40.4
|
63.7
|
92.2
|
149.9
|
201.7
|
249.5
|
300.2
|
398.6
|
461.7
|
|
Intake Temp (°C)
|
21
|
24
|
28
|
31
|
35
|
38
|
40
|
44
|
45
|
|
Exhaust Temp (°C)
|
26
|
30
|
32
|
37
|
41
|
45
|
48
|
54
|
59
|
|
Temp Rise (°C)
|
5
|
6
|
4
|
6
|
6
|
7
|
8
|
10
|
14
|
| Fan Voltage (V) |
4.6
|
5.0
|
5.4
|
6.3
|
7.2
|
8.2
|
9.1
|
11.0
|
11.0
|
| SPL (dBA@1m) |
21
|
22
|
23
|
26
|
29
|
31
|
34
|
37
|
37
|
|
Power Factor
|
0.93
|
0.95
|
0.96
|
0.98
|
0.97
|
0.98
|
0.99
|
0.99
|
0.99
|
|
NOTE: The ambient room temperature during testing
can vary a few degrees from review to review. Please take this into account
when comparing PSU test data.
|
ANALYSIS
1. VOLTAGE REGULATION was very good, within ±2% throughout the
test. Voltages tended to be slightly above nominal, but this is true of many
power supplies.
2. EFFICIENCY was also very good. The peak value of 81% was reached
between 200-300W output. The efficiency slope was quite steep at lower outputs,
and efficiency was not as good in the low end. However, in the range that most
systems will be operating, it was always above 70%. This is still good performance,
but a better results might be had from a power supply that is designed for lower
loads.
A comparison with the FSP Green PS shows that the shape of the efficiency curve
is almost identical, but the lower capacity of the Green PS means that it starts
at a higher efficiency and reaches its peak efficiency sooner.
3. POWER FACTOR was excellent thanks to the active power factor correction
circuit. Power factor stayed above 0.93 throughout the testing, which is very
close to the theoretical maximum of 1.0.
4. TEMPERATURE & COOLING
Like the Green PS, cooling performance was solid but unremarkable. The temperature
rise stayed close to 6°C through most of the usable output range. Above
300W output, the temperature rise increased significantly, but it never got
high enough that safety was a concern. The intake temperature always remained below 50°C, so the ZM-460APS
was running within its maximum operating temperature.
5. FAN, FAN CONTROLLER and NOISE
The fans in Zalman's past power supplies have not been especially quiet, but
this 120mm NMB-MAT fan is one of
the smoothest power supply fans we've heard. In fact, at its lowest speed, it
was smoother and quieter than the Seasonic S12. Considering that the S12s have the top spot for quiet fan-cooled PSUs, that's quite
a compliment.
At minimum speed, the fan was very close to inaudible; only a faint background
hum could be heard. The fan was obviously running very close to minimum speed
as a slight "chugging" could be heard at a close distance. As the
intake temperature increased, the hum gradually increased in intensity until
it was clearly audible with the intake temperature somewhere around 30°C.
Changes in pitch and intensity were very gradual.
Unfortunately, the fan controller in the ZM460-APS didn't quite meet the same standard as the fan, so it will probably be a little louder than
the Seasonic S12s in actual use. Even though it wasn't on par with the champ, it
was still not bad and is quite different from the controller in the Seasonic.
Most fan controllers stay at a single level until a certain thermal threshold
has been reached, when the fan speed begins to increase. The fan curve is basically a straight horizontal line which tilts upwards at the trigger temperature. Better PSUs
increase the fan speed over a longer period of time, and utilize good heatsinks to ensure that the maximum fan speed is not reached until
a very high output level. The advantage of the this design is that the fan tends
to stay at very low speed almost all the time.
Zalman's fan controller changes almost linearly with the intake temperature.
In general, this is not as good an approach as the hinged fan curve described above. In practice, changes in the Zalman's fan speed tended to be very, very slow. However,
it was always changing very slightly to compensate for slight changes in temperature,
so the sound was not as steady as other power supplies. Whether this fan noise variability is audible will depend on the rest of the system and on the ambient room noise.
Overall, the Zalman managed to stay below our arbitrary "quiet" level
of 30 dBA@1m until it reached 250W output ? albeit at a coolish 20°C room ambient, which probably helped a bit. This is still very good performance, and
a decided improvement over Zalman's previous effort.
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