Intel Pentium 4 Processor in the 478-PinPackage at 1.40 GHz, 1.50 GHz, 1.60 GHz, 1.70 GHz, 1.80 GHz, 1.90 GHz, and 2GHz

Electrical Specifications

Datasheet 11

2.0 Electrical Specifications

2.1 System Bus and GTLREF

Most Pentium 4 processor in the 478-pin package system bus signals use Assisted

Gunning Transceiver Logic (AGTL+) signalling technology. As with the Intel P6 family of

microprocessors, this signalling technology provides improved noise margins and

reduced ringing through low voltage swings and controlled edge rates. Like the Pentium 4

processor in the 423-pin package, the termination voltage level for the Pentium 4

processor in the 478-pin package AGTL+ signals is V

, which is the operating voltage of

the processor core. The use of a termination voltage that is determined by the processor

core allows better voltage scaling on the system bus for the Pentium 4 processor in the

478-pin package. Because of the speed improvements to data and address bus, signal

integrity and platform design methods have become more critical than with previous

processor families. Design guidelines for the Pentium 4 processor in the 478-pin package

system bus are detailed in the appropriate Platform Design Guide (refer to Ta bl e 1 ).

The AGTL+ inputs require a reference voltage (GTLREF) which is used by the receivers to

determine if a signal is a logical 0 or a logical 1. GTLREF must be generated on the

system board (see Table 12 for GTLREF specifications). Termination resistors are

provided on the processor silicon and are terminated to its core voltage (V

). Intel

chipsets will also provide on-die termination, thus eliminating the need to terminate the

bus on the system board for most AGTL+ signals.

Some AGTL+ signals do not include on-die termination and must be terminated on the

system board. See Table 3 for details regarding these signals.

The AGTL+ bus depends on incident wave switching. Therefore timing calculations for

AGTL+ signals are based on flight time as opposed to capacitive deratings. Analog signal

simulation of the system bus, including trace lengths, is highly recommended when

designing a system.

2.2 Power and Ground Pins

For clean on-chip power distribution, the Pentium 4 processor in the 478-pin package has

85 V

(power) and 181 V

(ground) inputs. All power pins must be connected to V

while all V

pins must be connected to a system ground plane.The processor V

pins

must be supplied the voltage determined by the VID (Voltage ID) pins.

2.3 Decoupling Guidelines

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

capable of generating large average 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. Care must be taken in the board design to ensure that the

voltage provided to the processor remains within the specifications listed in Tab le 6.