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

Dual Intel

Xeon™ Processor Voltage Regulator Down (VRD) Guidelines

1 Scope

This document details the guidelines for developing a single embedded voltage regulator circuit

(VRD) to supply the required current and voltage to the common power plane for two Intel

Xeon™ processors or Low Voltage Intel Xeon Processors on a dual-processor-capable system

board. The parameters specified in this document are provided as guidelines only. For the most

current processor specifications please refer to the appropriate component datasheet.

Intel Xeon processors have unique requirements for voltages supplied to them. Their bus

implementation, called AGTL+, the processor core, and the cache are being powered from the

same voltage supply. Figure 1 shows two possible power distribution scheme options for the

system board designer:

 Two plug-in voltage regulator modules (as defined in the VRM 9.0 or VRM 9.1 design

guidelines) operating in tandem with current-shared outputs and with one VRM per occupied

processor socket: that is, a 1:1 VRM-to-processor ratio

 A single VRD, as detailed in this document.

Power

Supply

Voltage Regulator Module 1

(refer to VRM9.0/9.1)

Voltage Regulator Module 2

(refer to VRM9.0/9.1)

Intel® Xeon

Processor

Intel Xeon Processor

Power

Supply

Voltage Regulator Down

Intel Xeon Processor

Figure 1 – Power Distribution Options

This document does not address system boards supporting in excess of two processors (i.e.,

Multiple Processor or MP systems). Intel expects MP systems to use voltage regulator modules

(VRM 9.1), with a 1:1 VRM-to-processor ratio. The Dual Intel Xeon Processor VRD and

VRM 9.1 are electrically equivalent: a processor requires either implementation and its related

power delivery design to deliver the same voltage and current to the processor’s socket.

Figure 2 illustrates a basic electrical model for a single VRD, dual-processor power delivery

approach, based on an Intel Xeon processor – Intel 860 chipset platform core design.