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THERMAL & ACOUSTIC TESTING
Aside from the i945GTt-VFA and the LC-12, only three other components were
needed to complete the system:
Windows XP Pro SP2 was installed, and our usual gamut of software tools installed:
- SpeedFan
4.31 for CPU and other hardware monitoring.
- Intel Thermal Analysis Tool for processor stress testing, thermal
monitoring, and throttle monitoring.
Other tools:
TEST RESULTS
Ambient conditions were 19°C and 18 dBA. It is Winter, and the
lab was snowed in under about 30 cm of snow when the testing was conducted.
This made for unusually cold, but also unusually quiet ambient conditions.
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AOpen i945GTt-VFA & Silverstone LC-12 Test Results
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Load Condition
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CPU Temperature
(via SpeedFan)
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CPU Core
Temperature
(via Intel TAT)
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System
Temperature
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HDD
Temperature
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Fan Speed
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System
Power Draw
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Noise Level
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Idle
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47°C
(49°C w/o
SpeedStep)
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33°C
(38°C w/o
SpeedStep)
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59°C
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38°C
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2700 RPM
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25W
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23 dBA@1m
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Load (Intel TAT)
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106°C*
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98°C*
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80°C
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50°C
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3600 RPM
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63W
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25 dBA@1m
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Load (Cover Removed)
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79°C
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73°C
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59°C
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31°C
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3600 RPM
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57W
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24 dBA@1m
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HDD Seek
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47°C
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33°C
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59°C
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40°C
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2700 RPM
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27W
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27 dBA@1m
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*CPU throttled at these temperatures.
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Testing the i945GTt-VFA and the LC-12 together was an exercise in steady nerves.
This system ran uncomfortably, even painfully hot, despite the wintery conditions
in our lab. If your gut instinct is to shut things down as soon as the processor
approaches 50°C, this is not the board for you; according to Speedfan (which
reported a different sensor than Intel's Thermal Analysis Tool), the CPU idled
at 47°C. This isn't a P4 Prescott we're talking about. This is a mobile
processor that idles at ~1.5W.
The "system" temperature (which we suspect is actually the Northbridge)
idled at 60°C!
And, the worst part of all this? The total power draw was just 25W. Folks,
the only systems we've measured with less heat output than that are VIA's
EPIA based systems. Even the
iMac couldn't match such a low power draw. When you have a 25W system that
runs at 50°C in idle, your thermal engineers have done something seriously,
seriously wrong.
Not surprisingly, the system throttled to keep cool under full load, even with
the CPU fan going full tilt. What was surprising was how long it took to throttle.
The CPU remained stable and fully functional right up to 98°C. We'll have
to rethink our ideas about what a safe CPU temperature is; Intel's new Core-series
chips appear to be more heat tolerant (or perhaps just report higher temperatures)
than the old Netburst-based ones. Whether or not the CPU is built to take such
a thrashing, other components are not, and the 80°C "system" temperature
and the 50°C hard drive were unacceptable.
After our nerve-wracking experience at 100°C, we were surprised to find
that the aluminum casing of the LC-12 was hot to the touch. When we popped the
cover off and felt the drive tray, it was too hot to touch for more than a second
or two. Ordinarily, the case material plays very little role in exhausting system
heat, but that was clearly not the case this time. Presumably, the lack of a
system fan and the tiny exhaust vents meant that heat had to use whatever means
necessary to dissipate, including conduction via the aluminum shell.
All this pointed to the case as the culprit for the high temperatures, so we
ran the test again without the cover. This dropped the CPU temperature by about
25°C — still high, but no longer dangerous. More significantly, the
system power draw dropped by 6W, indicating that the power circuitry was no
longer headed towards thermal runaway.
Thermal performance nonwithstanding, the tiny amount of power sipped up by
the i945GTt-VFA was impressive. When the board was running properly, the 57W
load was probably lower than any other Intel or AMD-based system we've tested,
though exact comparisons are difficult to make due to differences in stress
software (vs. the Shuttle X100)
and in components (the LCD in the
iMacs).
From a noise perspective, things turned out well enough. Despite the small
heatsink and the buzzy fan, AOpen surprised us with one of the best, most conservative
fan controllers we've ever encountered on a motherboard. Changes in fan speed
were very, very gradual, and could not be detected by ear unless listened for
specifically.
There were hints that the fan controller wasn't as simple as a thermal threshold.
When the system was initially powered up, the fan spun at full speed for about
five minutes before dropping slowly to minimum speed, where it stayed until
the system was pressed hard. We couldn't identify a positive threshold temperature
when the fan speeded up, but it seemed to start increasing when the CPU Core
was somewhere between 70~80°C.
The acoustic difference between minimum and full speed was not large, which
probably helped contribute to our perception that changes in fan speed were
difficult to hear. And, given how fast the fan was spinning (2,700~3,600 RPM),
the 23~25 dBA@1m noise measurements were actually pretty good. The noise was
acceptably quiet no matter what the speed, although it would never fall into
the inaudible category that the best systems achieve. Our biggest complaint
was that the noise character was unpleasant, with lots of buzz and whine that
was far from smooth.
The worst noise from the system actually had nothing to do with the fan at
all; seek noise from the hard drive was the most disruptive noise we heard.
The 27 dBA@1m is about accurate for what we heard. The seeks were sharp and
clearly audible above the rest of the system noise. That's very loud for a supposedly
"quiet" notebook drive, and much louder than the 20 dBA@1m seek noise
that we heard when we did our
original review. It was the effect of the aluminum box amplifying the vibrations
from the hard drive.
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