Intel Xeon Processor Multiprocessor Platform Design Guide

Mechanical and EMI Design Considerations

Intel recommends the following for constructing the mounting holes for the enabled retention

mechanism.

• All four RM mounting holes must have ground pad rings.

• Ground pad annular ring should be no less than 125 mils wide. Try to cover the entire keep-out

zone, if possible. See the following illustration for better dimensions.

• Place 8-12 vias in the annular ring, which connects the pad to internal ground planes.

• Anodizing or any form of insulated coating of the heat sink is strongly discouraged.

Refer to Figure 7-3 for specific details regarding the ground pads that are required to utilize this

reduction technique.

7.2 Electromagnetic Interference Considerations

7.2.1 Introduction

As microprocessor amperage and speeds increase, the ability to contain the corresponding

electromagnetic radiation becomes more difficult. Frequencies generated by these processors will

be in the low gigahertz (GHz) range, which will impact both the system design and the

electromagnetic interference (EMI) test methodology.

This section is intended to provide electrical and mechanical design engineers with information

that will aid in developing a platform that will meet government EMI regulations. Heatsink

grounding, processor shielding, differential and spread spectrum clocking and the test methodology

impact to FCC Class B requirements are specifically discussed.

Designers should be aware that implementing all the recommendations in this guideline will not

guarantee compliance to EMI regulations. Rather, these guidelines may help to reduce the

emissions from processors and motherboards and make chassis design easier.

Figure 7-3. Retention Mechanism Ground Ring

80 mils

15 mils

125 mils

RM Mounting

hole

Ground Rin

VIA