Intel E6540 HH80557PJ0534M User Manual

15

This chapter describes the electrical characteristics of the processor interfaces and 

signals. DC electrical characteristics are provided.

The processor has VCC (power), VTT and VSS (ground) inputs for on-chip power 

distribution. All power lands must be connected to V

CC

, while all V

SS

 lands must be 

connected to a system ground plane. The processor V

CC

 lands must be supplied the 

voltage determined by the Voltage IDentification (VID) lands. 

The signals denoted as V

TT

 provide termination for the front side bus and power to the 

I/O buffers. A separate supply must be implemented for these lands, that meets the 

V

TT

 specifications outlined in 

.

Due to its large number of transistors and high internal clock speeds, the processor is 

capable of generating large current swings. This may cause voltages on power planes 

to sag below their minimum specified values if bulk decoupling is not adequate. Larger 

bulk storage (C

BULK

), such as electrolytic or aluminum-polymer capacitors, supply 

current during longer lasting changes in current demand by the component, such as 

coming out of an idle condition. Similarly, they act as a storage well for current when 

entering an idle condition from a running condition. The motherboard must be designed 

to ensure that the voltage provided to the processor remains within the specifications 

listed in 

. Failure to do so can result in timing violations or reduced lifetime of 

the component. 

V

CC

 regulator solutions need to provide sufficient decoupling capacitance to satisfy the 

processor voltage specifications. This includes bulk capacitance with low effective series 

resistance (ESR) to keep the voltage rail within specifications during large swings in 

load current. In addition, ceramic decoupling capacitors are required to filter high 

frequency content generated by the front side bus and processor activity. Consult the 

Desktop LGA775 Socket.

Decoupling must be provided on the motherboard. Decoupling solutions must be sized 

to meet the expected load. To insure compliance with the specifications, various factors 

associated with the power delivery solution must be considered including regulator 

type, power plane and trace sizing, and component placement. A conservative 

decoupling solution would consist of a combination of low ESR bulk capacitors and high 

frequency ceramic capacitors.