AMD Thermal, Mechanical, and Chassis Cooling Design Guide Publication # 23794 Rev: H Issue Date: November 2002 (c) 2000-2002 Advanced Micro Devices, Inc. All rights reserved. The contents of this document are provided in connection with Advanced Micro Devices, Inc. ("AMD") products. AMD makes no representations or warranties with respect to the accuracy or completeness of the contents of this publication and reserves the right to make changes to specifications and product descriptions at any time without notice. No license, whether express, implied, arising by estoppel or otherwise, to any intellectual property rights is granted by this publication. Except as set forth in AMD's Standard Terms and Conditions of Sale, AMD assumes no liability whatsoever, and disclaims any express or implied warranty, relating to its products including, but not limited to, the implied warranty of merchantability, fitness for a particular purpose, or infringement of any intellectual property right. AMD's products are not designed, intended, authorized or warranted for use as components in systems intended for surgical implant into the body, or in other applications intended to support or sustain life, or in any other application in which the failure of AMD's product could create a situation where personal injury, death, or severe property or environmental damage may occur. AMD reserves the right to discontinue or make changes to its products at any time without notice. Trademarks AMD, the AMD Arrow logo, AMD Athlon, AMD Duron, and combinations thereof are trademarks of Advanced Micro Devices, Inc. Other product names used in this publication are for identification purposes only and may be trademarks of their respective companies. AMD Thermal, Mechanical, and Chassis Cooling Design Guide 23794H--November 2002 Table of Contents List of Tables . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . vii Revision History . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ix Summary of Requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 PGA Socket A-Based Processor Thermal Requirements . . . . . . . . . . 2 Socket Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Socket A-Based Processor Specifications . . . . . . . . . . . . . . . . . General Socketed Design Targets . . . . . . . . . . . . . . . . . . . . . . . Suggested Interface Materials . . . . . . . . . . . . . . . . . . . . . . . . . . Sample Socket A Heatsink Drawings. . . . . . . . . . . . . . . . . . . . . Socket A Heatsink Design Considerations . . . . . . . . . . . . . . . . 2 3 5 6 7 7 Socketed Motherboard Restrictions. . . . . . . . . . . . . . . . . . . . . 10 Thermocouple Installation for Temperature Testing . . . . . . . . . . . . 13 Chassis Cooling Guidelines . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16 Chassis Airflow . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16 Power Supply as Part of the Cooling Solution . . . . . . . . . . . . 17 Rules for Proper Cooling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19 Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20 iii AMD Thermal, Mechanical, and Chassis Cooling Design Guide iv 23794H--November 2002 23794H--November 2002 AMD Thermal, Mechanical, and Chassis Cooling Design Guide List of Figures Figure 1. Figure 2. Figure 3. Figure 4. Figure 5. Figure 6. Figure 7. Figure 8. Figure 9. Figure 10. Figure 11. Figure 12. Socket A . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 Dimensions of Socket A . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 Sample Drawing of Socket A Heatsink . . . . . . . . . . . . . . . 7 Heatsink and Load Pads . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 Motherboard Keepout Area for a Socket A AMD AthlonTM Processor Heatsink . . . . . . . . . . . . . . . . . 11 Motherboard Keepout Area for a Socket A AMD DuronTM Processor Heatsink . . . . . . . . . . . . . . . . . . 12 Measuring Thermocouple Position. . . . . . . . . . . . . . . . . . 13 Bottom View of Heatsink and Drill Depth. . . . . . . . . . . . 14 Injecting Thermal Grease into Drilled Hole . . . . . . . . . . 15 Installed Thermocouple. . . . . . . . . . . . . . . . . . . . . . . . . . . 15 Airflow through the Chassis . . . . . . . . . . . . . . . . . . . . . . . 16 Power Supply Venting . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18 v AMD Thermal, Mechanical, and Chassis Cooling Design Guide vi 23794H--November 2002 23794H--November 2002 AMD Thermal, Mechanical, and Chassis Cooling Design Guide List of Tables Table 1. Table 2. Table 3. Table 4. Table 5. Table 6. Table 7. List of Tables Socketed Processor Specifications for the AMD AthlonTM Processor Model 6 . . . . . . . . . . . . . . . . . . . Socketed Processor Specifications for the AMD AthlonTM Processor Model 8 . . . . . . . . . . . . . . . . . . . Socketed Processor Specifications for the AMD DuronTM Processor Model 7 . . . . . . . . . . . . . . . . . . . . General Socketed Thermal Solution Design Target for the AMD AthlonTM Processor Model 6 . . . . . . . . . . . . . General Socketed Thermal Solution Design Target for the AMD AthlonTM Processor Model 8 . . . . . . . . . . . . . General Socketed Thermal Solution Design Target for the AMD DuronTM Processor . . . . . . . . . . . . . . . . . . . . . Suggested Thermal Interface Materials . . . . . . . . . . . . . . 3 4 4 5 5 6 6 vii AMD Thermal, Mechanical, and Chassis Cooling Design Guide viii 23794H--November 2002 List of Tables AMD Thermal, Mechanical, and Chassis Cooling Design Guide 23794H--November 2002 Revision History Date Rev Description November 2002 H Updated values in Tables 1, 2, 3, 4, 5, and 6, and updated dimensions throughout. Added Fan Considerations section. Updated PS photos and updated airflow diagram. March 2002 G Updated Table 1 and Table 3 for total die size, Acore, and pthermal max values. January 2002 F Updated Figure 5, "Motherboard Keepout Area for a Socket A AMD AthlonTM Processor Heatsink," on page 11, removing the four mounting holes. November 2001 E Added Bergquist, Honeywell, Power Devices, and ShinEtsu to the list of Vendors in Table 7, "Suggested Thermal Interface Materials," on page 6. March 2001 D Corrected AthlonTM and DuronTM processor die sizes in tables 1 and 2 on page 4. February 2001 C Corrected Max. Length for heatsink from blank to 60mm, and corrected Min. Length for heatsink from 60mm to blank in Table 4 and in Table 6. October 2000 B May 2000 Revision History A Added mention of AMD Duron processor in the text and added the following tables and figures with AMD Duron information: Table 3 on page 4, Table 6 on page 6, and Figure 6 on page 12. Revised "Suggested Interface Materials" on page 6, and Table 7 on page 6. Added Section, "Thermocouple Installation for Temperature Testing" on page 13, and added Figure 7 through Figure 10. Initial release based on AMD Athlon Processor Family Thermal Cooling Requirements Version 2.1. ix AMD Thermal, Mechanical, and Chassis Cooling Design Guide x 23794H--November 2002 Revision History 23794H--November 2002 AMD Thermal, Mechanical, and Chassis Cooling Design Guide AMD Thermal, Mechanical, and Chassis Cooling Design Guide This document specifies performance requirements for the design of thermal, mechanical, and chassis cooling solutions for the AMD AthlonTM and AMD DuronTM processors. In addition to providing design targets, drawings are provided from an AMD-designed solution meeting the requirements of the AMD Athlon and AMD Duron processors. Summary of Requirements To a l l ow t he opt i ma l re l i ab il i t y fo r A MD A th l o n a nd AMD Duron processor-based systems, the thermal design solution should dissipate heat from a theoretical processor running at a given maximum thermal power. The following sections specify recommended values for these optimal thermal parameters. By setting a high-power target, the engineer may avoid redesigning a point solution heatsink/fan sink, thus increasing the life of the particular thermal solution. 1 AMD Thermal, Mechanical, and Chassis Cooling Design Guide 23794H--November 2002 PGA Socket A-Based Processor Thermal Requirements The first step to achieving proper thermal performance is to dissipate the heat generated by the processor. This, normally, is accomplished by use of a heatsink of some design. The following section includes the specifications required to have a proper heatsink design for Socket A processors. Socket Description Socket A is a PGA socket designed for socketed AMD AthlonTM and AMD DuronTM processors. Figure 1 shows the socket layout. Note: The figure socket is labeled SOCKET 462, which is synonymous with the Socket A. Figure 1. Socket A Socket A is very similar in form factor to previous sockets, such as Socket 7. Socket A incorporates additional pins in the inner portion of the socket. Thus, a thermal solution for Socket A can leverage preexisting design efforts. Figure 2 on page 3 details the physical dimensions of Socket A. 2 PGA Socket A-Based Processor Thermal Requirements AMD Thermal, Mechanical, and Chassis Cooling Design Guide 23794H--November 2002 Figure 2. Dimensions of Socket A Socket A-Based Processor Specifications Table 1, Table 2 on page 4, and Table 3 on page 4 list the thermal specifications of the socketed AMD Athlon and AMD Duron processors. Table 1. Socketed Processor Specifications for the AMD AthlonTM Processor Model 6 Symbol Max Value Tdie Description Maximum die temperature Total die size Die size 129.26 mm2 Includes L2 cache Acore Core area Die size not including L2 cache Form factor Heatsink form factor Max processor thermal power 105.72 mm2 PGA Pthermal Notes 90C 72.0 W PGA Socket A-Based Processor Thermal Requirements PGA Socket A form factor Required supported power 3 AMD Thermal, Mechanical, and Chassis Cooling Design Guide 23794H--November 2002 Table 2. Socketed Processor Specifications for the AMD AthlonTM Processor Model 8 Symbol Description Tdie Maximum die temperature Total die size Acore Die size Core area Max Value 90C 85C Notes For Model 2100+ and below For Model 2200+ and above 80.89 mm2 Includes L2 cache. For CPUID = 680 only. 84.66 mm2 Includes L2 cache. For CPUID = 681 only. 86.97 mm2 Includes L2 cache. For CPUID = 682 only. 67.35 mm2 Die size not including L2 cache. For CPUID = 680 only. Die size not including L2 cache. For CPUID = 681 only. Die size not including L2 cache. For CPUID = 682 only. PGA Socket A form factor 71.12 mm2 73.43 mm2 Form factor Pthermal Heatsink form factor Max processor thermal power PGA 68.4 W Required supported power Table 3. Socketed Processor Specifications for the AMD DuronTM Processor Model 7 Symbol Max Value Tdie Description Maximum die temperature Total die size Die size 105.68 mm2 Includes L2 cache Acore Core area Die size not including L2 cache Form factor Heatsink form factor Max processor thermal power 99.61 mm2 PGA Pthermal Notes 90C 60.0 W PGA Socket A form factor Required supported power General Socketed Design Targets To maintain the die temperature of the processor below the maximum T die value, certain heatsink design points must be considered. Table 4 details additional specifications that must be met for the AMD Athlon processor model 6 to reliably operate. Table 4. General Socketed Thermal Solution Design Target for the AMD AthlonTM Processor Model 6 Symbol 4 Description Min Max Notes PGA Socket A-Based Processor Thermal Requirements AMD Thermal, Mechanical, and Chassis Cooling Design Guide 23794H--November 2002 Table 4. General Socketed Thermal Solution Design Target for the AMD AthlonTM Processor Model 6 L W H CFM mHS Length of heatsink Width of heatsink Height of heatsink Fan airflow Fclip Clip force TA 60 mm 63 mm 80 mm 64 mm 16 cfm Mass of heatsink Measurements are for the entire assembly, including attached fan. Minimum 16 cfm airflow 300 g 12 lb Inside the box local ambient temperature 24 lb Typical F: 14 lb F 18 lb Nominal F = 16 lb 42C Table 5 details additional specifications that must be met for the AMD Athlon processor model 8 to reliably operate. Table 5. General Socketed Thermal Solution Design Target for the AMD AthlonTM Processor Model 8 Symbol L W H CFM mHS Fclip TA Description Length of heatsink Width of heatsink Height of heatsink Fan airflow Min 60 mm 16 cfm Mass of heatsink Clip force Max 63 mm 80 mm 64 mm Notes Measurements are for the entire assembly, including attached fan. Minimum 16 cfm airflow 300 g 12 lb Inside the box local ambient temperature 24 lb* Typical F: 18 lb F 22 lb Nominal F = 20 lb 42C Notes: * Clip force as high as 30 lb is acceptable if using a 6-tab clip. PGA Socket A-Based Processor Thermal Requirements 5 AMD Thermal, Mechanical, and Chassis Cooling Design Guide 23794H--November 2002 Table 6 shows the thermal solution design target for the AMD Duron processor. Table 6. General Socketed Thermal Solution Design Target for the AMD DuronTM Processor Symbol L W H CFM mHS Fclip TA Description Length of heatsink Width of heatsink Height of heatsink Fan airflow Min 60 mm Max 63 mm 80 mm 64 mm 16 cfm Mass of heatsink Notes Measurements are for the entire assembly, including attached fan. Minimum 16 cfm airflow 300 g Clip force 12 lb Inside the box local ambient temperature 24 lb Typical F: 14 lb F 18 lb Nominal F = 16 lb 50 C Suggested Interface Materials AMD evaluates thermal interface materials for socketed designs. A list of suggested materials tested by AMD is provided in Table 7. If the heatsink needs to be removed, the phase change material must be replaced on the heatsink before re-installing the heatsink. Use a plastic scraper to gently remove the old phase change material from the heatsink. Table 7. Suggested Thermal Interface Materials Vendor Bergquist Chomerics Honeywell Power Devices ShinEtsu Thermagon Interface Material HF225UT T725 PCM45 Powerfilm PCS-TC-11T-13 T-pcm905C Material Type Phase Change Phase Change Phase Change Phase Change Phase Change Phase Change Sample Socket A Heatsink Drawings Figure 3 provides a reference drawing of a heatsink AMD has designed to work with Socket A processors. 6 PGA Socket A-Based Processor Thermal Requirements AMD Thermal, Mechanical, and Chassis Cooling Design Guide 23794H--November 2002 Measurements are in millimeters Figure 3. Sample Drawing of Socket A Heatsink Socket A Heatsink Design Considerations Heatsink design considerations include the characteristics of the heatsink itself, the clip used to hold the heatsink to the processor, the thermal interface material between the heatsink and the processor, and the length of the fan wire for active heatsinks. Heatsink Considerations The important design parameters of the socket A heatsink include the dimensions of the flat base, the maximum base footprint, and the clearance over the socket cam. Flat base to contact support pads. The PGA processor is housed in a 50 x 50 mm ceramic package. The heatsink makes direct contact w i t h t h e f l i p -c h i p d i e . W h i l e t h e d i e d i m e n s i o n s a re considerably less than the 50 mm x 50 mm package footprint, the heatsink base must maintain a minimum flat surface of 46 mm x 46 mm centered on the package and 48 mm x 48 mm at a maximum. This positioning is required for the heatsink to make contact with compliant load support pads. The pads protect the die from mechanical damage during heatsink PGA Socket A-Based Processor Thermal Requirements 7 AMD Thermal, Mechanical, and Chassis Cooling Design Guide 23794H--November 2002 installation, as well from shock and vibration. Figure 4 details the ceramic package and compliant load support pads. TM Figure 4. Heatsink and Load Pads Maximum base footprint of 63 mm x 80 mm. T h e m a x i m u m b a s e footprint for socket heatsinks is 63 mm x 80 mm (as detailed in Figure 3 on page 7). Not all processor speeds require the full 63 mm x 80 mm footprint. Heatsinks with approximately 60 mm x 60 mm footprints have proven to be adequate for low to moderate clock frequencies. Clearance in heatsink base for socket cam box. The heatsink base must have enough clearance so that it does not contact the cam box on the socket. The clearance zone is defined in the example shown in the Figure 3 on page 7 and Figure 4. Clip Considerations The important design parameters of the socket A heatsink clip include the load applied to the heatsink, where the load is applied, how the clip ensures the location of the heatsink in relation to the processor package and socket, and ease of installation. 8 PGA Socket A-Based Processor Thermal Requirements AMD Thermal, Mechanical, and Chassis Cooling Design Guide 23794H--November 2002 Load target of 16 lb with range of 12-24 lb. The clip load is greater than that allowed for previous pro cessors with similar mechanical form factors. Table 4 on page 4 details the clip force requirements. Load applied directly over center of die (asymmetric design). To e n s u re adequate thermal interface performance between the flip-chip die and the heatsink, the clip must apply its load to the heatsink along a single contact axis. The load should be applied 26.8 mm from the front (non-cam side) socket tab load point (see Figure 4 on page 8). The acceptable tolerance for off-center clip load is 1.5 mm. Feature to lock relative position of heatsink, clip, and socket. A l o c k i n g feature is needed to avoid incorrect placement of the heatsink on the package. Such a lock can be constructed with small tabs that project from the sides of the clip and fit into a heatsink channel. Installation features designed to minimize operator fatigue. The clip load requirements of the socketed processor are significantly higher than past models. Emphasis should be focused on providing a clip design that is easily installed. While clips that do not require tools for installation offer some advantages, designs that accept a flat-head screwdriver (or nutdriver) near the clip hook have certain advantages. Such advantages include the ability to pry the clip hook over the socket tab during installation and the ability to install the clips onto the tabs in areas that are tightly confined by motherboard components surrounding the socket. Thermal Interface Considerations Many customers have indicated a preference for pre-applied thermal interface materials. A heatsink vendor that chooses to offer pre-applied interface materials should apply a 25 x 25 mm pad centered 25 mm from the front edge of the heatsink. PGA Socket A-Based Processor Thermal Requirements 9 AMD Thermal, Mechanical, and Chassis Cooling Design Guide 23794H--November 2002 Fan Considerations An active heatsink design incorporates a fan mounted to the heatsink. To ensure that the heatsink fan wire can reach power connectors on all Socket 462-based boards, the fan wire length should be at least 8 inches. Socketed Motherboard Restrictions The motherboard design and layout must meet certain restrictions to ensure that the socketed thermal solution does n o t i m p e d e t h e p e r fo r m a n c e o f c o m p o n e n t s o n t h e motherboard. To maintain adequate airflow around the microprocessor, certain areas on the motherboard must be free of projecting components. Figure 5 on page 11 shows these keepout areas on the motherboard for a n AMD Athlon processor, and Figure 6 on page 12 shows the motherboard keepout area for an AMD Duron processor. 10 PGA Socket A-Based Processor Thermal Requirements AMD Thermal, Mechanical, and Chassis Cooling Design Guide 3 4 2 23794H--November 2002 Figure 5. Motherboard Keepout Area for a Socket A AMD AthlonTM Processor Heatsink PGA Socket A-Based Processor Thermal Requirements 11 AMD Thermal, Mechanical, and Chassis Cooling Design Guide 23794H--November 2002 Figure 6. Motherboard Keepout Area for a Socket A AMD DuronTM Processor Heatsink 12 PGA Socket A-Based Processor Thermal Requirements AMD Thermal, Mechanical, and Chassis Cooling Design Guide 23794H--November 2002 Thermocouple Installation for Temperature Testing To i n s t a l l a t h e r m o c o u p l e t o m e a s u re t h e o p e ra t i n g temperature of the heatsink, perform the following procedure: 1. Mark a location on the base of the heatsink as shown in Figure 7. Determine the position of the thermocouple hole using the following measurements: * a = 24.765 mm * b = caliper measurement * If the heatsink extends over the PGA processor (as it is diagrammed), then x = a + b * If the heatsink does not extend over the PGA processor, then x = a - b * y = 2 mm Drill hole Die Figure 7. Measuring Thermocouple Position Thermocouple Installation for Temperature Testing 13 AMD Thermal, Mechanical, and Chassis Cooling Design Guide 23794H--November 2002 2. Drill a hole at the marked location using a #53 drill bit (1.5113 mm or 0.0595 inches). If the heatsink is symmetric in relation to the processor package, drill to a depth of half the width of the heatsink. If it is not symmetrical to the processor, drill to a depth that is directly over the center of the die, as shown in Figure 8. Figure 8. Bottom View of Heatsink and Drill Depth 14 Thermocouple Installation for Temperature Testing AMD Thermal, Mechanical, and Chassis Cooling Design Guide 23794H--November 2002 3. Inject thermal grease into the newly drilled hole with a syringe as shown in Figure 9. Use Dow Corning 340 white thermal grease or it's equivalent. Figure 9. Injecting Thermal Grease into Drilled Hole 4. Gently insert the thermocouple into the hole until it bottoms out, and tape it down with Kapton tape, making sure not to kink the thermocouple. Figure 10 shows an installed thermocouple. Figure 10. Installed Thermocouple Thermocouple Installation for Temperature Testing 15 AMD Thermal, Mechanical, and Chassis Cooling Design Guide 23794H--November 2002 Chassis Cooling Guidelines As high-performing systems continue to evolve, the power consumption of system components such as the processor, hard disk drives, and video cards continues to increase. The associated rise in power consumption can cause the system operating temperature specifications to be exceeded. The correct operating temperature of each system device can be controlled by providing proper airflow through the system case. Chassis Airflow System cooling is dependent on several essential and related factors. Figure 11 shows a typical mid-tower chassis with the internal physical characteristics and recommended airflow. Case 0 1 Desirable Airflow Power Supply Rear Exhaust Fan Exhaust Fan (80mm or greater) Bottom Inlet Power Supply Exhaust Fan (80mm or greater) Approximately .5"-1", (12mm-25mm) T2 Internal Ambient Air Rear View Side View T1 External Ambient Air Figure 11. Airflow Through the Chassis 16 Chassis Cooling Guidelines 23794H--November 2002 AMD Thermal, Mechanical, and Chassis Cooling Design Guide Using thermal couples (type K or T, 36 gauge) in the locations shown in Figure 11, temperatures T1 and T2 can be measured. T1 represents the external ambient air temperature. T2, which is located approximately 0.5 inch to 1.0 inch away from the processor fan (centered on the hub), represents the internal local ambient air temperature. It is highly recommended that T2 not exceed 40C. The following equation shows how to derive the proper overall system operating temperature: T = T2 - T1 T 7C to ensure proper cooling Power Supply as Part of the Cooling Solution For full-tower or mid-tower cases, it is important for system designers to be aware of the characteristics of the power supply used. Designers should only use a power supply intended for use with the AMD Athlon or AMD Duron processors. Consult with your power supply vendor to verify suitability. For best results, use a power supply with venting in the processor region, which means that the primary air intake is on the bottom of the power supply, usually with a secondary intake at the front of the power supply. For the purposes of this chapter, a power supply with bottom air intake is referred to as a n ATX-style power supply. Some power suppli es have NLX-style venting (the only air intake is at the front of the power supply). These power supplies do not pull significant amounts of air from the processor area. Figure 12 on page 18 compares desirable power supply venting designs with designs that are less desirable. The front and rear designs for the desirable and less desirable versions are very similar (the differences depend on the brand). However, the bottoms of the more effective power supply designs incorporate an air intake. Power supply having bottom air intakes typically cool the processor more effectively. Bottom air intakes with fans normally provide even more effective cooling. Chassis Cooling Guidelines 17 AMD Thermal, Mechanical, and Chassis Cooling Design Guide Desirable Version 23794H--November 2002 Less Desirable Version Front-- For the front air intake, the desirable and less desirable versions often are similar. Any differences depend upon the specific brand. Rear-- For the rear air intake, the desirable and less desirable versions are essentially the same. Differences depend upon the specific brand. Bottom-- On the bottom, the desirable version has an air intake. A bottom air intake typically cools the processor more effectively. If the bottom air intake has a fan, cooling is enhanced. Figure 12. Power Supply Venting 18 Chassis Cooling Guidelines AMD Thermal, Mechanical, and Chassis Cooling Design Guide 23794H--November 2002 Rules for Proper Cooling The following basic rules for chassis cooling can provide adequate airflow and system temperatures: Use the proper heatsink for the processor speed used in the system. Make sure that the heatsink has appropriate sized fan(s). For the AMD-recommended choices, just go to www.amd.com/systemconfig and see the AMD AthlonTM Processor Thermal Solutions pages or the AMD DuronTM Processor Recommended Cooling Solutions pages. (Go to the processor configuration sections and then choice the appropriate pages.) Use only the AMD-recommended thermal interface materials listed in Table 7 on page 6. Typically, AMDrecommended heatsinks include a validated thermal compound. If you are replacing the heatsink's packaged compound, use only AMD-recommended thermal materials. Use an auxiliary exhaust rear chassis fan. The suggested size is 80 millimeters or larger. The fan intake should be near the location of the processor. For best results, use an ATX power supply with air intake venting in the processor region, which means that the primary air intake is on the bottom of the power supply, not at the front of the power supply. Supplies with NLX-style venting (the primary air intake is at the front of the power supply) do not pull air from the processor area. Make sure all the internal wires and cables are routed carefully so airflow through the case is not blocked or hindered. Using tie-wraps to contain loose items can help. Many cards, such as AGP cards, generate heat. Either leave the slot next to these cards open, or use a shorter card in these slots to allow airflow around heat producing cards (typically those cards with many electrical components). High-speed hard drives, especially 10,000+ RPM SCSI hard drives, produce a great deal of heat. You can mount these drives in 5.25 inch frames and install them in the larger drive bays. This mounting allows greater airflow around the drives for better cooling. A front cooling fan is not essential. In some extreme situations, testing has actually shown that these fans can recirculate hot air rather than introducing cool air. Maintain a T 7C. Chassis Cooling Guidelines 19 AMD Thermal, Mechanical, and Chassis Cooling Design Guide 23794H--November 2002 Conclusion Thermal, mechanical, and chassis cooling solutions that meet the criteria described in the previous pages have been successful for applications incorporating AMD processors. AMD encourages vendors to innovate and propose other designs. If different heatsink production technologies, whether extrusion, folded fin, bonded fin, or cold forged, produce similar or better results than the solutions suggested in this guide, then designers are encouraged to incorporate them into new thermal solution designs. Any design, however, must meet the overall goal of dissipating the heat produced by the processor at a given ambient temperature. 20 Conclusion