Intel 830 2

Datasheet 15

Electrical Specifications

2Electrical Specifications

This chapter describes the electrical characteristics of the processor interfaces and signals. DC

electrical characteristics are provided.

The Intel® Pentium® D processor has 226 VCC (power) and 273 VSS (ground) inputs for on-chip

power distribution. All VCC lands must be connected to the processor power plane, while all VSS

lands must be connected to the system ground plane. The processor VCC lands must be supplied

with the voltage determined by the processor Voltage IDentification (VID) lands.

The Pentium D processor has 24 signals that are denoted as VTT that 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 VTT specifications outlined in Table 2 -3.

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

generating large current swings between low and full power states. This may cause voltages on

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

storage (CBULK), 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 Tabl e 2-3. Failure to do so can result in timing

violations or reduced lifetime of the component. For further information and design guidelines,

refer to the Voltage Regulator Down (VRD) 10.1 Design Guide For Desktop LGA775 Socket.

VCC 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 Voltage Regulator Down (VRD) 10.1 Design Guide For

Desktop LGA775 Socket for further information.

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.