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TEST METHODOLOGY
This sturdy modified LX-6A19 (D8000) case from Cool Cases became our test system housing.
For this review, we designed a
graphics card testing methodology that we hope to use in future reviews. It is an in-system
test, designed to determine whether the card is capable of being adequately
cooled in a low-noise system. By adequately cooled, we mean cooled well enough so 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 shutdown 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.
The test system was built around a midrange Pentium 4 Northwood processor
as an example of a mid-powered system that is fairly easy to keep quiet.
The system is used for our heatsink reviews, so we are already intimately
familiar with the thermal characteristics of the processor and motherboard.
Test Platform
- Intel
P4-2.8A The Thermal Design Power of this P4-2.8 (533
MHz bus) is 68.4 or 69.7W depending on the version. As the CPU is a demo model
without normal markings, it's not clear which version it is, so we'll round
the number off to ~69W. The Maximum Power, as calculated by
CPUHeat
& CPUMSR, is 79W.
- AOpen
AX4GE Max motherboard - Intel 845GE Chipset; built-in VGA. The on-die
CPU thermal diode monitoring system reads 2°C too high, so all readings are
compensated up by this amount.
- Scythe Shogun heatsink, cooled by a Nexus 120mm fan undervolted
to 7V.
- OCZ
DDRAM PC-4000, 512 MB
- Seagate Barracuda IV 40G 1-platter drive, sitting on foam in the
bottom of the case
- Antec Neo HE 430
ATX12V 2.01 compliant power supply
- Modified LX-6A19 (D8000) case from Cool Cases, outlined in detail below
- Nexus 120mm fan controlled by a variable voltage fan controller
Measurement and Analysis Tools
- CPUBurn
processor stress software
- RTHDRIBL
graphics demo to stress the GPU
- 3DMark05
benchmark software, used as an alternate means of stressing the GPU
- SpeedFan
version 4.25 software to show CPU temperature
- Seasonic Power Angel AC power meter, used to measure the power consumption
of the system
- A custom-built variable DC power supply that allows us to dial in exactly
what voltage is powering the system fan
System airflow is quite good, allowing the CPU and system fans to run at close
to inaudible speeds without compromising system cooling. The intake is about
the size of a 120mm fan. The only restriction is an air filter. A much more
restrictive cover for the filter was removed because it impeded the airflow
too much.
The one and only intake...
...and the same view, with the bezel removed.
There are two points of exhaust: The 120mm case fan, which will be run at a
number of different speeds, and the 80mm fan in the Neo HE power supply. The
case fan can be expected to exhaust the bulk of the heat, since the
Neo HE is unlikely to ramp up even at the maximum power draw that the test
system is capable of. The amount of airflow through the system can be controlled
by adjusting the speed of the case fan, thereby giving us a way of controlling
how difficult the thermal environment inside the case is.
Only two possible points of exhaust: The orange case fan and the fan in
the power supply.
The airflow in our test rig is typical of an ATX case. Air flows in through
the intake near the bottom of the front panel, and is pulled up to the top rear
corner. Most of this air will bypass the expansion cards altogether, but a small
amount will be pulled across the rear of the card as it is pulled between the
CPU heatsink and the case fan. The bulk of the air will be pushed through the
CPU heatsink.
The air will flow from the lower right to the upper left, drawing a small
amount of air across the VGA card.
Thermal testing consisted of running CPUBurn and RTHDRIBL simultaneously to
generate as much heat as possible. An initial test was run with the system fan
running at 12 volts, and then the fan was progressively slowed down to make
the thermal environment more difficult.
Because no thermal monitoring was available on the GV-N66256DP, CPU temperature
was used to determine when the temperature had stabilized. Once the temperature
was determined to be stable, the stress software was left running for at least
another 20 minutes while we watched the screen carefully for visual
artifacts that might indicate overheating. The last test, with the system fan
running at 5 volts, was left running for more than an hour.
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