Intel Pentium 4 672 HH80547PG1122MH User Manual

8

   
 

(4X data transfer rate, as in AGP 4X). Along with the 4X data bus, the address bus can deliver 
addresses two times per bus clock and is referred to as a ‘double-clocked’ or 2X address bus. In 
addition, the Request Phase completes in one clock cycle. Working together, the 4X data bus and 
2X address bus provide a data bus bandwidth of up to 3.2 Gbytes/second (3200Mbytes/sec). 
Finally, the system bus also introduces transactions that are used to deliver interrupts.

Signals on the system bus use Assisted GTL+ (AGTL+) level voltages which are fully described in 
the Intel

 850 Chipset Platform Design Guide.

A ‘#’ symbol after a signal name refers to an active low signal, indicating a signal is in the asserted 
state when driven to a low level. For example, when RESET# is low, a reset has been requested. 
Conversely, when NMI is high, a nonmaskable interrupt has occurred. In the case of signals where 
the name does not imply an active state but describes part of a binary sequence (such as address or 
data), the ‘#’ symbol implies that the signal is inverted. For example, D[3:0] = ‘HLHL’ refers to a 
hex ‘A’, and D[3:0]# = ‘LHLH’ also refers to a hex ‘A’ (H= High logic level, L= Low logic level).

“System bus” refers to the interface between the processor and system core logic (a.k.a. the chipset 
components). The system bus is a interface to the processor, memory, and I/O. For this document, 
“system bus” is used as the generic term for the Pentium 4 processor bus.

Commonly used terms are explained here for clarification:

•

 4 Processor in the 423-pin Package—The entire product including 

processor core, integrated heat spreader, and interposer.

•

Pentium 4 processor—Throughout this document “Pentium 4 processor” refers to the Intel

 4 Processor in the 423-pin Package.

•

Interposer —The structure on which the processor core package and I/O pins are mounted.

•

Processor core —The processor’s execution engine. All AC timings and signal integrity 
specifications are to the silicon of the processor core.

•

Integrated heat spreader —The surface used to make contact between a heatsink or other 
thermal solution and the processor. Abbreviated as IHS.

•

423-Pin Socket —The connector which mates the Pentium 4 processor to the system board.

•

Retention mechanism —The support structure that is mounted on the system board to 
provide added support and retention for heatsinks.

•

OLGA (Organic Land Grid Array) Package —Microprocessor packaging using “flip chip” 
design, where the processor is attached to the substrate face-down for better signal integrity, 
more efficient heat removal and lower inductance.