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31684 Rev. 3.00 September 2004
Builder’s Guide for AMD Athlon™ 64 Processor-
Based Desktops and Workstations
seam could cause an EMI problem. Spring fingers or foam EMI gasket can be used to seal these
gaps or seams.
8. Processor Heatsink Grounding
Although grounding of the processor heatsink has not yet been required on any AMD Athlon™ 64
processor-based systems, grounding of the processor heatsink can further lower the harmonic EMI
levels of the processor. Many AMD Athlon 64 processor-based motherboards contain grounding
pads around the footprint area of the processor. These grounding pads can be utilized to ground
the heatsink to the motherboard ground.
If excessive system level EMI radiated emissions exist after attempting all the listed EMI
reduction techniques, then more extensive remedies may be necessary. First, determine if the
emissions emanate from the system I/O cables (including the AC power cord) or from aperture
leaks in the system chassis. If EMI emissions emanate from a particular I/O cable, then improved
filtering or cable shielding may be required on that cable. If EMI emissions emanate from slots or
seams in the chassis enclosure, use copper tape across the apertures to improve shielding
effectiveness. If copper tape reduces emission levels to a satisfactory level, then chassis sheet
metal changes or conductive EMI gasketing can be added at that location.
Chapter 5
EMI Reduction Techniques 39