16 Datasheet
Electrical Specifications

2.2.3 FSB Decoupling

The Pentium D processor package integrates signal termination on the die as well as incorporates
high frequency decoupling capacitance on the processor package. Decoupling must also be
provided by the system baseboard for proper GTL+ bus operation.
2.3 Voltage Identification
The Voltage Identification (VID) specification for the Pentium D processor is defined by the
Voltage Regulator Down (VRD) 10.1 Design Guide For Desktop LGA775 Socket. The voltage set
by the VID signals is the reference VR output voltage to be delivered to the processor VCC lands
(Section 2.5.3 for VCC overshoot specifications). Refer to Table2-10 for the DC specifications for
these signals. A minimum voltage for each processor frequency is provided in Table 2 -3.
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 Table 2 -3.
The Pentium D processor uses six voltage identification signals, VID[5:0], to support automatic
selection of power supply voltages. Table 2 -1 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 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 LGA775 Socket for more details.
The processor provides the ability to operate while transitioning to an adjacent VID and its
associated processor core voltage (VCC). 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.
Minimum and maximum voltages must be maintained as shown in Tabl e 2-4/Ta ble 2-5 and
Figure 2-1/Figure 2-2 as measured across the VCC_SENSE and VSS_SENSE lands.
The VRM or VRD utilized must be capable of regulating its output to the value defined by the new
VID. DC specifications for dynamic VID transitions are included in Table 2 -3, Tabl e 2-4, and
Table 2 -5. Refer to the Voltage Regulator Down (VRD) 10.1 Design Guide For Desktop LGA775
Socket for further details.