 |
|
|
|
|
Please note: Do It Yourself articles and guides are intended for technically advanced users. Please review important cautionary information at the end of this page. Republished articles presented in the Do It Yourself section do not necessarily reflect the opinions or positions of AMD.
A Guide to System Thermals
It’s not unusual to ask, "What’s the right temperature to give me the best performance from my processor?" That’s a logical question. But there is more to know if you’re aiming for optimum system operation.
What might be an average or normal temperature on one system may not be normal on another system. This is because the thermals of any given system depend in large part on the system configuration. There are several high heat generating devices in modern systems. Video cards, processors, chipsets, hard drives, DVD drives, and high speed CD-ROM drives all generate a great deal of heat. Properly dissipating the heat build-up inside the case is essential to maintaining a stable system. Several components must be considered for proper cooling.
Heatsinks
Thermal Interface Materials
Cases and Components
Air Flow
Tips for Reducing Heat Buildup
Heatsinks
The primary purpose of any heatsink is to draw heat from the heat-generating device. Heatsinks can be found on several components inside a computer system. Processors, video cards, and chipsets are the main components that use heatsinks.
Heatsinks work because they use highly thermally conductive materials such as aluminum, copper, and nickel, and create a large surface area. Heat will always travel from the source and radiate out toward the cooler areas; this is why large surface areas are an important part of the heatsink design.
Heatsinks are a passive form of cooling, as they have no moving parts and require no power. However, passive cooling is rarely sufficient to properly cool a modern system.
In most cases, heatsinks are used in conjunction with fans. The addition of a fan makes the heatsink/fan (HSF) combination an Active Cooling solution. A fan’s effectiveness is often measured in CFMs (Cubic Feet per Minute), which determines how much air a fan can move in a given period. Higher CFM's means more airflow across the heatsink and, therefore, better cooling. However, the higher the CFM, the more noise is generated. The number of CFM's a fan can move is determined in large part by the speed of the rotation (in RPMs), the number and surface area of the fan blades, the size of the fan, and the pitch (or angle) of the blades.
Since most video cards and chipsets will already have the HSF installed, it is not necessary to worry about selecting the proper solution for these devices. The manufacturer will have already taken care of that aspect during design of the component. However, it might be necessary to select a proper HSF for the processor, which should be done with great care. Refer to the manufacturer’s website or contact them directly for a list of recommended solutions.
Note: This guide does not cover any aspects of water cooling or other active solutions, an in-depth topic that deserves its own guide.
Thermal Interface Materials
Thermal Interface Materials (TIM’s) are highly thermally conductive materials that help transfer heat from one device (typically a source device) to another (typically a HSF).
Whenever two surfaces come into contact with each other, there are microscopic air bubbles between the surfaces. Because air is a poor thermal conductor, filling these bubbles with a highly thermally conductive material will help improve the efficiency of the overall solution.
There are many types of thermal materials, from Phase Change Material (PCM) to thermal tape to thermal grease. Thermal tape is rarely recommended, as it typically is not suited for processor applications. PCM or grease are the more common materials used on modern processors.
Each solution has its advantages and disadvantages. Greases are often more thermally conductive, but they tend to be more difficult to work with and create more mess. Many types of grease are also electrically conductive or capacitive and can short out the processor if they come into contact with any surface mounted components on the processor package. PCM is usually preinstalled but is good only for one use. Once the heatsink is removed after the processor has been powered on, the material needs to be replaced.
Since PCM is usually preinstalled on the heatsink, there is no need to worry about using the proper amount. If a replacement PCM pad is required, it will usually come in a 1x1-inch square pad so, again, the amount has been determined. However, the old pad should be completely removed from the heatsink before the new pad is applied.
When working with thermal greases (or pastes), care should be taken not to use too much. Some people think that if a little is good, then a lot should be great. This is the wrong approach. Too much thermal grease will act as a blanket, trapping heat inside the processor. Use no more than the size of a grain of rice, spread evenly over the center of the heatsink. Again, care should be taken not to get it all over the processor package. The processor could short out if the grease is electrically conductive or capacitive and it gets onto the processor bridges or passive components on the processor package. Likewise, the grease should never come into contact with the processor pins.
Note: PCM is not recommended for AMD Athlon™ 64 or AMD Athlon 64 FX systems due to the strong adhesion created between the processor and the heatsink.
Cases and Components
Case size is another important component that plays a significant role in the thermal properties of any system. In addition to providing room for expansion components, large cases typically allow for better cooling, because more air circulates through the case.
A good case should allow for both intake and exhaust fans to be installed in the system. However, large cases take up more space on or under your desktop.
There are several form factors to choose from when selecting a case; most cases will typically support ATX, uATX (micro ATX), and mini ATX type motherboards. And smaller cases may not support ATX boards, since they are larger than the uATX or mini ATX standards.
As mentioned earlier, the number and type of components in your system will also play a role in the thermal properties. The more components installed, the more heat generated inside the system. This will drive up the ambient temperature inside the case. The higher the ambient temp, the more difficult it will be for HSFs to do their jobs.
Air Flow
In a typical desktop tower form factor, air should flow in from the bottom front of the case and exhaust out the top rear of the case. Ambient air temperatures inside the case will play a large role in the effectiveness of individual solutions used for the processor, video card, and chipset. Therefore, expelling excess heat is essential for proper cooling and stability.
As mentioned, a good case will usually allow for 1-2 intake fans (case fans) and 1-2 exhaust fans to assist with air circulation for proper cooling. In some high end cases, there could also be places to install fans on the side case panel as well as in the top of the case. Keep in mind, the more fans installed the better the cooling, but the more noise generated.
The goal should be to create negative air flow, with more air leaving the case than coming in. Typically, this is done by having more exhaust fans than intake fans. If a case has two intake fans at the front and two exhaust fans in the rear, then negative air flow is achieved because the power supply also has one exhaust fan.
Generally speaking, expansion slot fans are not a good idea because they will exhaust the cool air straight out the back of the case.
On rare occasions, an expansion slot fan may be needed, but it is usually not recommended.
Tips for Reducing Heat Buildup
If a system is running hot, here are a few tips on how to cool it down.
- Make sure the system is using a high quality heatsink/fan.
- Avoid hot spots by spacing out high heat generating devices or cards.
- Make sure the processor voltage is correct. Many overheat conditions can be traced back to incorrect voltage settings.
- Install case fans (if not already installed in case).
- Use high quality TIM.
- Keep airflow clean by using rounded cables, or tie off cables so airflow is not restricted.
- Do not block intake vents/fans or place the case inside cabinets.
- Routinely, blow out dust from inside the case. In addition to being charged particles, dust can act like a blanket on top of your components, trapping heat inside.
This list, while not all-inclusive, will help in many overheating conditions.
Cautionary Statement
Activities and projects described herein may involve the use of tools and materials that may present health and safety hazards. These must be handled carefully and all tools and products should be used strictly according to manufacturers' precautions and instructions for the safe use of the respective tool or product. The techniques described herein may result in the voiding of manufacturers' warranties. The user assumes all risks associated with the techniques described in this article/guide. THIS INFORMATION IS PROVIDED “AS IS” WITH NO WARRANTY, EXPRESS OR IMPLIED. AMD ASSUMES NO RESPONSIBILITY FOR ANY ERRORS CONTAINED IN THIS ARTICLE/GUIDE AND HAS NO LIABILITY OR OBLIGATION FOR ANY DAMAGES ARISING FROM OR IN CONNECTION WITH THE USE OF THIS ARTICLE/GUIDE.
|
|
|
|
|
