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TEST METHODOLOGY
Full details of our latest VGA test system is detailed in a recent article. Our test procedure is an in-system test to determine whether the
cooler is adequate for use in a low-noise system. By adequately cooled,
we mean cooled well enough that no misbehavior related to thermal overload is
exhibited. Thermal misbehavior in a graphics card can show up in a variety of
ways, including:
- Sudden system shutdown or reboot without warning.
- Jaggies and other visual artifacts on the screen.
- Motion slowing and/or screen freezing.
Any of these misbehaviors are annoying at best and dangerous at worst —
dangerous to the health and lifespan of the graphics card, and sometimes to
the system OS.
Test Platform
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The exterior view of our test platform.
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The Antec P180 case has two front 120mm intakes — the bottom one feeds
fresh air to the hard drive and power supply section while the top one allows
airflow into the rest of the system. The stock filter and door over the intake
vent for the main chamber are removed — replaced with the metal mesh for
the top panel 120mm fan. The filter for the lower PSU/HDD chamber is retained,
but its cover door is also removed to reduce airflow impedance. The front door
is cast away as well to improve airflow. The top three optical drive bays are
covered with a block of open-cell foam which allows some air to flow in but
also absorbs much of the internal sound from coming out.
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The internals of our new testbed.
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The processor is cooled by a modified Gigabyte G-Power 2 Pro without its plastic
shroud utilizing a Scythe Slip Stream 120mm 500RPM fan, connected directly to
the motherboard's CPU fan header — it is completely inaudible. Above it,
a block of foam is positioned on the ceiling over top fan vent, which also draws
some air in when the system is running.
The only system fan is a Nexus 120mm mounted in the rear exhaust position with
silicon rubber nubs made expressly to reduce vibration conduction into the case.
It is powered by the PSU through to a customized fan speed controller using
zener diodes. A knob protruding from the wall of foam at the front allows the
fan voltage to be easily varied.
The power supply is a Seasonic S12-600 with the stock fan replaced by a Scythe
Slip Stream 120mm 800RPM fan, hard-wired to run at 5V. The fan just barely starts
up, and spins extremely slowly, at ~400RPM. Air expelled from the PSU is only
mildly warm, even during long sessions of high power testing.
The notebook hard drive is suspended in the lower drive bay with zip ties and
cloth elastic with a 2mm round cross-section. No vibration from the drive can
be felt on the drive bay. Foam is attached to both sides of the compartment
divider as an extra silencing measure.
The overall noise level of the system is excellent at only ~19 dBA@1m with
the system fan @ 7V. For comparison, during the quietest moments in our lab
with all the computers turned off, the ambient noise level is around 17 dBA.
Measurement and Analysis Tools
- ATI Tool
version 0.26
as a tool for stressing the GPU and to show GPU temperature
- CPUBurn
P6 processor stress software.
- SpeedFan
version 4.33 to show CPU temperature
- Seasonic
Power Angel AC power meter, used to monitor the power consumption
of the system
- A custom-built internal variable fan speed controller to power the
system fan
- A custom-built external variable fan speed controller to power the
VGA heatsink fan (if applicable)
- Bruel & Kjaer (B&K) model 2203 Sound Level Meter, used to
accurately measure SPL (sound pressure level) down to 20 dBA and below.
Heatsinks are installed on an ATI Radeon X1950XTX (if compatible) — a high-powered
video card that features a thermal sensor built into the GPU core. The accuracy
of the sensor is unknown. The video memory heatsink is usually left on unless
it interferes with the VGA cooler.
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Our test card: a Radeon X1950XTX.
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Our main test consists of ATI Tool's artifact scanner running in conjunction
with CPUBurn to stress both the graphics card and processor simultaneously.
It is a realistic test that mimics the stress on the CPU and GPU produced by
a modern video game, only more consistently. The software is left running until
the GPU temperature stabilizes for at least 10 minutes at which point, both
the CPU and GPU temperatures are recorded. In addition we also take measurements
of the system's overall noise level and power consumption using a B&K Sound
Meter and a Seasonic Power Angel respectively. If the heatsink has a fan, the
procedure is repeated at various fan speeds while the system fan is left at
the lowest setting of 7V. If it is a passive cooler, the system fan instead
is varied to study the effect of system airflow on the heatsink's performance.
If artifacts are detected in ATI Tool or other instability is noted, the heatsink
is deemed inadequate to cool the video card in our test system. Usually artifacts
begin to appear when the GPU temperature reaches between 90°C and 95°C.
Preliminary testing is also done at idle, and with only CPUBurn running for
comparison. For idle results, the system is left stagnant for 10 minutes before
ATI Tool is loaded and the first temperature it reports is used. We do this because
on our test platform, after ATI Tool is loaded, it puts some kind of stress on
the GPU, causing the temperature to climb immediately (even if it is left idle
for hours beforehand) and the power consumption to increase by approximately
10W. We theorize that initially the card is in 2D mode, either underclocked
or undervolted (or possibly both) and that ATI Tool automatically puts it in
3D mode, which would account for the rise in temperature and power draw. ATI Tool
is left running in the background for the remainder of testing which is why
the GPU temperature during CPUBurn will appear higher compared to idle. Consider
this the difference between 2D idle and 3D idle.
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