Performance Results And Interesting Interactions
Test Setup and Measurement Methods
In order to ensure comparable conditions (like ambient temperature) for the measurements, we set up our lab with a slight, circulating, indirect airflow. This helps to remove excess heat. A fan on the far end of the room directs the air and lets it circulate along the walls. With this, we can guarantee a constant ambient temperature around our test subject, preventing a bubble of hot air from forming around the card.
We conduct our measurements at temperatures between 64°F (18°C) and 75°F (24°C). We slightly heat up the room in 2°C steps, so that we can compare how the ambient affects the card's temperature, including its surface-mounted components. The GPU may be one target for good cooling, but it is just one of many. Parts like the memory modules and VRMs are almost always ignored in other tests, to the detriment of their long-term health.
Of course, it's also necessary to measure clock rate, fan speeds, and (if possible) power consumption in order to get a truly objective result.
- Differences in temperature can only be exact if the measurements are taken under identical conditions
- All components need to be included in the measurements, not just the GPU
- All sensors need to be monitored and their values logged (fan speeds, frequencies, etc.)
Be Careful with Target Temperatures!
Assume we take our test subject and let the card run free. At first glance, the GPU temperatures are certain to disappoint us because there is hardly any apparent difference. Comparing the original slippery goop to the expensive drop of luxury yields a tie, more or less.
But let's take a closer look at our logs, particularly the fan speeds. The impact we so painfully missed out on just a moment ago now hits us forcefully. There's a roughly 300 RPM difference between the stock card and the cooler with Kryonaut between it and the GPU. Our ears are as happy as can be.
But don't start the victory dance just yet; there is a downside to this, too. In general, manufacturers tend to use the fan curve as their default remedy for high temperatures. As a consequence, in the absence of increased airflow, some parts of the card start to get a little hot.
This is further proof that fan profiles don't just rely on corresponding GPU temperatures. Fan speeds are the result of many other factors as well, such as preset target temperatures, which overrule the fan curve settings since the temperature target has priority.
While the VRMs and GPU package stay at roughly the same temperature, the passively cooled memory modules that rely on steady airflow run into a thermal problem. They're now operating two degrees Kelvin above their specified maximum temperatures.
Now's a good time to point out that the temperature values some tools list as VRM (or VRM1, VRM2, etc.) are nothing short of fiction; none of the currently-available graphics cards even have MOSFETs with temperature sensors! At most, these measurements represent an "aux temperature" the PWM controller chip measures for its own benefit. Except that this chip is already heating up quite a bit, plus its position on the PCB is usually miles away from the actual VRMs.
And so we adjust the fan curve and force the card to use the same rotational speeds we saw originally. Increased airflow pushes the temperatures down significantly, allowing us to rest easy knowing all of the components are sufficiently cooled.
- Target temperatures in the BIOS may heavily influence measurement results
- Fan speeds that are too low may cause components to overheat
- There is no software that can read the actual VRM temperatures.
Maxing Out the Target Temperature
With this setting, the fan curve keeps the upper hand across most of the temperature range, and it's easy to see where it might make sense to invest money (or perhaps not). Furthermore, we also learn that with increasing room temperature, the difference narrow. Finally, we can conclude that the factory's assembly job was bad enough that even at 194°F (90°C), the card hits its limit.
While the most expensive thermal paste yields the best result, our thermal readings are no more than one degree Kelvin lower compared to Gelid's GC Extreme. There is a difference of up to four degrees Kelvin, however, compared to Arctic's MX-2 and the manufacturer's paste (applied correctly). In fact, the MX-2 is even worse than XFX's industrial paste. Consider this stuff a thing of the past. While it might still work for CPUs with more surface area and TDPs up to around 100W, it has no place between modern GPUs and their heat sinks.
The bottom line is that even for a mainstream card like XFX's Radeon RX 470, it can be worthwhile to replace the original thermal paste, even if a maximum of 150W measured during our stress test is relatively modest.
The higher the thermal power loss and the higher the difference in temperature between the card's surface and the cooling medium (air or water), the more you stand to gain in cooling performance from lower thermal resistance. However, cited differences of seven degrees Kelvin or more between factory and aftermarket thermal pastes are likely the result of several factors coming together, and no indication of a miracle paste.
At this point, we'll spare you a long list of formulas and stick with the simplified facts. There are no magic products, and physics doesn't make special exceptions. There is, however, focused, precise work and the application of slightly better thermal paste that might get you close to an ideal outcome, but will never solve your thermal problems on its own. That is, an above-average thermal paste won't turn a below-average cooler into a high-end solution.
- Target temperatures can be handled more flexibly when using better thermal pastes
- Performance gains depend on the thermal difference between the surface of the GPU heat spreader and the cooling medium
- The higher the amount of excess heat, the more important the choice of a good paste can be
We will see shortly that addressing other hot spots can also improve the total cooling performance of a graphics card. It isn't just the GPU that needs to be optimized.
MORE: All Graphics Content
MORE: All Cooling Content