Dual Intel Xeon Processor Voltage Regulator Down (VRD) Design Guidelines

Dual Intel
®
Xeon™ Processor Voltage Regulator Down (VRD) Guidelines
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2.1.4 Single or Dual Processor Operation
Many OEMs require that a dual-processor VRD supplying a Intel Xeon processor’s or Low
Voltage Intel Xeon processor’s common voltage plane operate with either one or two processors
installed on the board: i.e., the design must meet the static and transient voltage characteristics of
both the dual- and single-processor load lines. A solution is to adjust the load line for the
number of installed processors. OEMs who want jumper-free systems can do this with logic that
detects the presence of processors in each of the sockets and selects resistor combinations to
produce the right slopes. For example: no processors (00) = disable VRD; one processor (01 or
10) = single-processor load line; both processors (11) = dual-processor load line.
2.1.5 No-Load Operation
The VRD should operate in a no-load condition: i.e., with no processor installed. The VRD does
not need to meet the output regulation specifications described in section 2.1, but its output must
not exceed 110% of the value of the maximum VID output voltage, and it must not trigger over-
voltage fault detection circuitry.