Intel Pentium D 945 HH80553PG0964MN User Manual

16

The processor integrates signal termination on the die. In addition, some of the high 

frequency capacitance required for the FSB is included on the processor package. 

However, additional high frequency capacitance must be added to the motherboard to 

properly decouple the return currents from the front side bus. Bulk decoupling must 

also be provided by the motherboard for proper [A]GTL+ bus operation. 

The Voltage Identification (VID) specification for the processor is defined by the Voltage 

Socket. The voltage set by the VID signals is the reference VR output voltage to be 

delivered to the processor VCC pins (see 

 for V

CC

 overshoot 

specifications). Refer to 

 for the DC specifications for these signals. A minimum 

voltage for each processor frequency is provided in

.

Individual processor VID values may be calibrated during manufacturing such that two 

devices at the same core speed may have different default VID settings. This is 

reflected by the VID Range values provided in 

. Refer to the Intel

Specification Update for further details on specific valid core frequency and VID values 

of the processor. Note that this differs from the VID employed by the processor during 

a power management event (Enhanced Intel SpeedStep

®

 technology or Enhanced 

HALT State). 

The processor uses 6 voltage identification signals, VID[5:0], to support automatic 

selection of power supply voltages. 

 specifies the voltage level corresponding to 

the state of VID[5:0]. A ‘1’ in this table refers to a high voltage level and a ‘0’ refers to 

a low voltage level. If the processor socket is empty (VID[5:0] = x11111), or the 

voltage regulation circuit cannot supply the voltage that is requested, it must disable 

itself. See the Voltage Regulator-Down (VRD) 10.1 Design Guide For Desktop and 

Transportable LGA775 Socket for further details.

The processor provides the ability to operate while transitioning to an adjacent VID and 

its associated processor core voltage (V

CC

). This will represent a DC shift in the load 

line. It should be noted that a low-to-high or high-to-low voltage state change may 

result in as many VID transitions as necessary to reach the target core voltage. 

Transitions above the specified VID are not permitted. 

 includes VID step sizes 

and DC shift ranges. Minimum and maximum voltages must be maintained as shown in 

 as measured across the VCC_SENSE and VSS_SENSE lands.

The VRM or VRD used must be capable of regulating its output to the value defined by 

the new VID. DC specifications for dynamic VID transitions are included in 

 and 

. Refer to the Voltage Regulator-Down (VRD) 10.1 Design Guide For Desktop 

and Transportable LGA775 Socket for further details.