Intel Xeon Processor Multiprocessor Platform Design Guide

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Mechanical and EMI Design Considerations
7.2.10 EMI Test Capabilities
FCC regulations in the United States specify the maximum test frequency for products with clocks
in excess of 1 GHz is 5 times the highest clock frequency or 40 GHz, which ever is lower. OEMs
are advised to inquire into the capabilities of their preferred EMC test lab to ensure they are able to
scan up to the required frequency range.
History indicates that processor performance and frequency double approximately every two years.
With this in mind, it would be advisable to be prepared for the frequencies that will need to be
scanned in the next few years.
Since the FCC Rules ultimately require testing to 40 GHz, commercial test equipment has been
developed which is capable of making measurements to that frequency. Although it will be some
time before processors require testing at this frequency, it may be cheaper to upgrade to 40 GHz
now rather than making several intermediate steps.
It is also possible to upgrade various parts at different times. The spectrum analyzer may be
upgraded to 40 GHz today while only obtaining the necessary antennas to support the initial
processor frequencies. As processor speed increases, the necessary antennas and cables could be
purchased which would support testing to the higher levels. Cost flexibility in antenna selection is
probably the greatest, as different antenna designs are necessary for different frequency ranges.
7.2.11 Summary
High-speed clock frequencies within the platform will make EMI compliance more challenging. In
order to facilitate successful chassis and motherboard designs, Intel has developed a number of
components and techniques to reduce or contain EMI emissions. OEMs are advised to verify that
their preferred EMC test facility is capable of measuring the required frequencies.