Temperature and Overclocking Testing

Cooler Testing Methods

To best gage the quality of the GPU cooler under review, GPU temperature was taken with the graphics card idle and under load. To replicate GPU idle conditions, the system was rebooted and allowed to sit idle for 30 minutes. To replicate a stress graphics load, EVGA OC Scanner X was run over a 30 minute period using the Furry E (GPU memory burner::3072MB) 3D Test, a 1280×1024 resolution, and an 8x MSAA Antialiasing setting. After each run, the system was shut down and allowed to rest for 30 minutes to cool down. This procedure was repeated a total of 12 times – six times for the stock speed runs and six times for the overclocked speed runs.

Temperature measurements were taken directly from the GPU thermistors using TechPowerUp GPU-Z v0.8.2. For both the idle and load temperatures, the highest recorded value in the application were used for the run. Note that the temperature values are reported as deltas rather than absolute temperatures with the delta value reported calculated as GPU temperature – ambient temperature.

To adequately measure the EVGA GTX 970 SC's cooler performance, performance testing was done for all scenarios under two operational conditions – air cooled using the ACX 2.0 cooler, and liquid cooled using the modified configuration with the HeatKiller GPU-X3 GPU water block. During the tests with the modified card, it ws found that a minimal amount of airflow was needed blowing across the VRM heat sinks to prevent card instabilities.

Note that the temperature values are reported as deltas rather than absolute temperatures with the delta value reported calculated as GPU temperature – ambient temperature. For all tests, room ambient temperature was maintained between 24-26C. Sound measurements of the system cooler where taken with the sound meter placed 3 feet away from the system with all other devices in the room silenced. The Sound Meter Pro applet on a Samsung Galaxy S5 mobile phone was used to measure decibel level.

Stock Temperature Testing

The graphics card temperature testing was conducted at stock speeds with air-based and liquid-based cooling.

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EVGA did a very good job in designing the ACX 2.0 cooler for the GTX 970 SC video card with it able to keep the temperatures to the upper 60s, low 70s under stress testing (assuming an ambient temperature of 25C). The idle temperature measurements are a bit high, but keep in mind that the ACX 2.0 cooler fans do not spin until the GPU reaches 60C. Adding the HeatKiller GPU-X3 Core GPU block to the card drops temps immensely with the spread between idle and load temperatures a mere 6C. The measured GPU temperature of a mere 10C over ambient is nothing short of impressive.

Overclocked Temperature Testing

Using the EVGA Precision X 16 v5.3.3 tweaking software, the graphics card was overclocked to its highest stable settings using air-based and liquid-based cooling. For details on the overclocked settings used for testing and benchmarks, please see the Manual Overclocking section below. Note that the card required use of the Agressive fan mode through the Precision X 16 software to keep the GPU and VRM stable throughout all runs.

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At overclocked speeds, the temperature differences between the air-cooled GPU and liquid-cooled GPU are not as dramatic from a pure numbers standpoint – 26C over ambient with air cooling and 12C over ambient with liquid cooling. However, the ACX 2.0 cooler required use of the Aggressive fan preset within the Precision X 16 software to maintain card stability, adding unnecessary fan noise to the mix while running through the stress test. The real strength in the liquid cooled configuration comes with the reduced fan noise and the minimal 9C delta between the idle and load temperatures.

Stock settings

Stock with ACX 2.0 cooler

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With its stock ACX 2.0 cooler, the GTX 970 SC graphics card maintained a 1354MHz GPU Boost Clock speed and a 7012MHz memory speed while under load with a maximum GPU voltage of 1.2000V.

Stock with HeatKiller GPU-X3 Core GPU block

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Once HeatKiller GPU-X3 Core GPU block was added to the card (in addition to the copper sinks on the VRMs and memory modules as well as a 120mm fan directing air flow over the sinks), something magical happened to the card's GPU Boost clock rate and GPU voltage under load. At stock settings, the card's internal logic auto-boosted the GPU Boost Clock by +40MHz to 1392MHz and the GPU voltage to 1.2120V without any user manipulation using the Precision X 16 software. Not too shabby for the simple act of liquid cooling the GPU. Do note that this 40MHz boost in GPU core speed made little difference in the stock benchmark numbers, which is why only a single set is shown on the Benchmarks page.

Manual Overclocking

Using water-based cooling on a graphics card has a direct effect on the operating temperature of the cooled components because of the coolant's more efficient heat absorption properties in comparison with air-based heat dissipation. The lower operating temperature of the graphic card's components indirectly effects the card overclocking potential, allowing the card to attain faster performance because of the liquid coolant's more efficient heat dissipation. For testing the full potential of the GTX 970 SC card, overclocking threshold testing was performed with the card operating in air-cooled only mode using the stock ACX 2.0 cooler and in liquid-cooled mode using the HeatKiller GPU-X3 Core GPU block.

For both overclocking tests, EVGA's Precision X 16 tweaking software (v5.3.3) was used to enable the settings with TechPowerUp GPU-Z (v0.8.2) used to validate the settings properly took effect. Graphics card stability was tested by performing a full run through the FutureMark 3DMark Fire Strike benchmark with a 1920×1080 resolution without crash or artifacting. Once the 3DMark Fire Strike benchmark run stabilized, card stability was checked using the Unigine Heaven, Grid 2, and Metro: Last Light in-game benchmark tests. The settings were further refined until no artifacting or crashes occurred in any of those applications. To further ensure card operational reliability at the configured settings, the card was torture tested over an extended period with EVGA OC Scanner X using the Furry E (GPU memory burner::3072MB) 3D Test, a 1280×1024 resolution, and an 8x MSAA Antialiasing setting.

Air-cooled Overclocking Results

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Using the GTX 970 SC's stock ACX 2.0 air-based cooler, we were able to get the card stable at a GPU boost clock speed of 1479 MHz (+125) with a memory speed of 7808 MHz (+400).

EVGA Precision X 16 profile settings

  • GPU Clock Offset – +125MHz
  • Memory Clock Offset – +400MHz
  • GPU Voltage Overvoltage – +12mV (Max)
  • Power Target – 110% (Max)
  • GPU Temperature Target – 91C (Max)
  • Fan Preset – Aggressive

Performance numbers

  • GPU Boost Clock Speed – 1479MHz
  • Memory Speed – 7808MHz
  • GPU voltage – 1.2000V

Liquid-cooled Overclocking Results

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Running the GTX 970 SC card with the modded configuration and the HeatKiller GPU-X3 Core GPU water block placed in-line with the Raystorm CPU block, we were able to increase the GPU boost clock and memory speeds to 1542 MHz (+150) and 8004 MHz (+500). The GPU boost clock was actually increased by +190MHz over the stock air-cooled settings if you figure in the free +40MHz boost that the card experienced at stock with the addition of the GPU block. This translates to a 50% increase in the GPU boost clock settings and a 20% increase in memory clock settings over the overclock settings achieved with the ACX 2.0 cooler by adding the GPU block, memory sinks, and backplate to the card.

EVGA Precision X 16 profile settings

  • GPU Clock Offset – +150MHz
  • Memory Clock Offset – +500MHz
  • GPU Voltage Overvoltage – +25mV (Max)
  • Power Target – 110% (Max)
  • GPU Temperature Target – 91C (Max)
  • Fan Preset – N/A

Performance numbers

  • GPU Boost Clock Speed – 1542MHz
  • Memory Speed – 8004MHz
  • GPU voltage – 1.2120V

Sound Testing

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At stock speeds, the noise generated by the ACX 2.0 cooler cannot be beat. The cooler does not even spin up the fans until the GPU hits 60C. Even at temperatures above 60C, the ACX 2.0 cooler is virtually silent. The strength of the HeatKiller GPU-X3 Core GPU water block comes into play while overclocking. The fan speed and generated noise does not increase at all, while the ACX 2.0 cooler must use a steep fan curve to maintain stability (as shown in the Precision X 16 screen shot of the fan settings). The water cooled system was virtually silent compared to the building crescendo of the GPU fans. However, the fans were able to maintain the card at a respectable temperature under load despite the additional fan noise.

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