VGA Coolers: Thermalright V1 Ultra, Zalman 700 & 900, AC Silencer 5 v.3

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This sturdy modified LX-6A19 (D8000) case from Cool Cases housed our test system.

Our test procedure is an in-system test, designed 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.

The test system was built around the coolest Intel Prescott-based processor we had on hand. It's a reasonable example of a mid-powered system that is fairly easy to keep quiet. Almost all AMD-based processors should run cooler than our Pentium 520, and almost all Intel-based desktop processors run hotter.

Test Platform

  • Intel 520 processor (P4-2.8 Prescott, 1Mb cache, 800 MHz FSB in 775 casing). The combined power draw for the processor and the VRMs on the test motherboard was measured at 85.3 watts. Intel's official TDP is 84 watts.
  • AOpen i945Ga-PHS motherboard - Intel i945Ga Chipset; built-in VGA.
  • CoolerMaster Hyper 48 heatsink, cooled by a Nexus 92mm fan undervolted to 7V.
  • Corsair DDR2 RAM, 1024 MB
  • Seagate Momentus 5400.2 120 GB, 2-platter drive, suspended in a NoVibes III just inside the front intake vent.
  • Antec Neo HE 430 ATX12V 2.01 compliant power supply, with a custom-built fresh air duct to ensure that the internal fan did not ramp up during testing.
  • Modified case from Cool Cases, outlined in detail below.
  • Nexus 120mm fan controlled by a variable voltage fan controller.

Measurement and Analysis Tools

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 is only one point of exhaust: The 120mm case fan, which can be run at a number of different speeds. The 80mm fan in the Neo HE power supply was taken out of the picture by using a custom-built duct to ensure that the fan never ramped up. 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.

A fresh air duct isolates the power supply from the rest of the system.

Only one possible point of exhaust: The orange case fan.
The fan in the power supply draws its air from a duct that does not interact with the rest of the system airflow.

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 towards the CPU heatsink and the case fan. All of the air will exit the case via the exhaust fan.

The air will flow from the lower right to the upper left, drawing a small amount of air across the VGA card.

The coolers were installed on an AOpen Aeolus PCX6800GT-DVD256 — a medium-powered video card that features a thermal sensor build into the GPU core. The accuracy of the sensor is unknown, but it is good enough to make relative judgments between the various coolers.

This GeForce 6800GT has stood up to a year's worth of abuse around the SPCR lab.

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