Understanding the Basics
Processors, the heart of any computing device, are responsible for executing instructions and performing calculations. As processors work, they generate heat due to electrical resistance and energy dissipation within their circuits. This heat is a byproduct of the billions of transistors switching on and off rapidly.
The Impact of Heat on Performance
- Thermal Throttling: When a processor gets too hot, it initiates a process called thermal throttling. This means it automatically reduces its clock speed to lower the temperature, which leads to slower performance. Thermal throttling is a protective measure designed to prevent permanent damage to the processor.
Figure 1: Raspberry Pi 3B+ CPU speed and temperature during a ten-minute power- intensive synthetic workload and is followed by a five-minute cooldown. Raspberry Pi 3B+ quickly reaches the point of 60°C point, designed to prevent the SoC hitting the maximum limit of 80°C (source: https://www.raspberrypi.com/).
- Electrical Resistance: High temperatures increase electrical resistance in the processor’s circuits. This can cause errors in computation and reduce the overall efficiency of the processor, further slowing down its operation.
- Material Degradation: Prolonged exposure to high temperatures can degrade the materials within the processor. Over time, this can lead to reduced performance and a shorter lifespan for the processor.
- Voltage Droop (Vdroop): High processor temperatures can lead to a phenomenon called “voltage droop” or “Vdroop.” Vdroop refers to a decrease in the core voltage supplied to the processor when it operates at high temperatures. This reduction in core voltage occurs to mitigate the effects of the temperature on the processor’s stability.
- Increased Error Rates: High processor temperatures can cause an increase in the error rates of the processor. The increased temperature can lead to subtle changes in the electrical properties of the transistors and other components within the processor. These changes can result in errors in calculations and data transmission.
Limitations of Current Technology
Currently, most consumer-grade processors rely on passive cooling methods, primarily heatsinks and fans. While these methods are effective to a certain extent, they have limitations:
- Heatsinks: Heatsinks absorb heat from the processor and dissipate it into the surrounding air. However, their effectiveness is limited by the surface area of the heatsink and the ambient air temperature. Beyond a certain point, heatsinks cannot cool the processor any further.
- Fans: Fans improve the efficiency of heatsinks by moving air across their surfaces, carrying heat away. Despite this, fans can only reduce the temperature to a level slightly above the ambient temperature. They are also prone to wear and noise, and their effectiveness diminishes if airflow is obstructed or if they become clogged with dust.
Figure 2: CPU heatsink-fan combo
- Phase Change Cooling: Phase change cooling involves a coolant that changes phases (from liquid to gas) to absorb heat. This method is often used in high-end cooling solutions. However, phase change cooling has limitations due to the effects of ambient temperatures, the size of the cooling apparatus, and the handling of liquids. These factors make it less practical for widespread consumer use.
Figure 3: CPU phase change cooler. Coolant inlet and outlet are clearly visible.
The Potential of Active Cooling
Active cooling solutions are emerging as a promising alternative to traditional cooling methods. These solutions actively lower the processor’s temperature rather than merely facilitating heat dissipation. One of the most effective active cooling methods involves directly cooling the processor core.
- Liquid Cooling: Liquid cooling systems use a liquid coolant that circulates through a loop, absorbing heat from the processor and dissipating it through a radiator. This method is more efficient than air cooling because liquids have a higher heat capacity than air. However, liquid cooling is complex, contains liquids that pose a risk of leaks, demands a lot of energy, and is not always suitable for directly cooling the processor core or for many applications.
- Peltier Coolers: Peltier coolers, or thermoelectric coolers, use the Peltier effect to create a heat flux between the junction of two different types of materials. They can directly cool the processor core by transferring heat away more efficiently than passive methods. However, Peltier coolers are relatively large compared to the size of the processor, have poor efficiency, and their physical properties limit their use in many scenarios.
Innovations in Active Cooling: SolidT’s Approach
SolidT is developing a thin-film active cooling device based on the Peltier effect. With a thickness of microns and a heat transfer coefficient (QC) and high coefficient of performance (COP), SolidT’s solution can be a game changer and set a benchmark in processor active cooling. By attaching SolidT’s micro cooling unit to the processor hot spot, SolidT will enable efficient cooling of the processor core. This innovation addresses and overcomes the limitations mentioned above:
- Complexity: SolidT’s solution is designed to be thin and straightforward to integrate, reducing the complexity typically associated with active cooling systems.
- Energy Consumption: With high QC, SolidT’s device promises better energy efficiency, lowering operational costs and power demand.
- Efficiency: By attaching SolidT’s solution only to the CPU’s hotspot, the efficiency is significantly increased. Instead of wasting energy to cool the entire CPU surface, SolidT’s solution delivers the heating energy directly from the hotspot to the dissipation area. This targeted approach reduces the hotspot temperature with a relatively small amount of energy, making the cooling process more efficient.
- Space and Size Constraints: The micron-scale thickness of SolidT’s cooling film ensures it fits within the compact form factors of modern devices.
- Risk of Leakage: As a solid-state solution, SolidT’s device eliminates the risks associated with liquid coolants.
- Cost: By improving efficiency and reducing complexity, SolidT’s solution can potentially lower the overall cost of active cooling systems.
Advantages of Active Cooling
- Enhanced Performance: By maintaining lower temperatures, active cooling prevents thermal throttling, allowing the processor to operate at higher clock speeds for longer periods. This translates to better performance, especially in demanding tasks like gaming, video editing, and scientific computing.
- Improved Reliability: Lower operating temperatures reduce the risk of material degradation and electrical resistance issues. This improves the reliability and longevity of the processor.
- Greater Overclocking Potential: For enthusiasts and professionals who overclock their processors to achieve higher performance, active cooling provides the necessary thermal headroom to push the processor beyond its rated specifications safely.
Conclusion
As processors continue to evolve and demand more power, the need for effective cooling solutions becomes increasingly critical. While passive cooling methods like heatsinks, fans, and phase change cooling have their limitations, active cooling techniques offer a path forward. By directly cooling the processor core, active cooling can maintain lower temperatures, prevent thermal throttling, and ensure optimal performance. SolidT’s innovative thin-film cooling solution addresses many of the current limitations of active cooling systems, paving the way for more powerful, efficient, and reliable computing solutions in the future.