Gigabyte GV-N66256DP Fanless Graphics Card

Graphics Cards
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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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