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Technical Reference Guide 361834-002 3-3
Processor/Memory Subsystem
Figure 3-2 illustrates the internal architecture of the Intel Pentium 4 processor.
Figure 3-2. Pentium 4 Processor Internal Architecture
The Intel Pentium 4 increases processing speed by using higher clock speeds with
hyper-pipelined technology, therefore handling significantly more instructions at a time. The
Pentium 4 features a branch prediction mechanism improved with the addition of an execution
trace cache and a refined prediction algorithm. The execution trace cache can store 12 kilobytes
of micro-ops (decoded instructions dealing with branching sequences) that are checked when
re-occurring branches are processed. Code that is not executed (bypassed) is no longer stored in
the L1 cache as was the case in the Pentium III.
The front side bus (FSB) of the Pentium 4 uses a 200-MHz clock but provides bi- and
quad-pumped transfers through the use of 2x- and 4x-MHz strobes. The Pentium 4 processor is
compatible with software written for x86 processors.
3.2.2 Processor Upgrading
All units use the LGA775 ZIF (Socket T) mounting socket. These systems require that the
processor use an integrated heatsink/fan assembly. A replacement processor must use the same
type heatsink/fan assembly as the original to ensure proper cooling.
The processor uses a PLGA775 package consisting of the processor die mounted “upside down”
on a PC board. This arrangement allows the heat sink to come in direct contact with the processor
die. The heat sink and attachment clip are specially designed provide maximum heat transfer
from the processor component.
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CAUTION: Attachment of the heatsink to the processor is critical on these systems. Improper attachment
of the heatsink will likely result in a thermal condition. Although the system is designed to detect thermal
conditions and automatically shut down, such a condition could still result in damage to the processor
component. Refer to the applicable Service Reference Guide for processor installation instructions.
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CAUTION: Installing a processor that is not supported by the system board may cause damage to the
system board and/or the processor.
Pentium Type Core Speed ALU Speed FSB Speed L2 Cache Size
P4 560
3.60 GHz 7.2 GHz 800 MHz 1 MB
P4 550
3.40 GHz 6.8 GHz 800 MHz 1 MB
P4 540
3.20 GHz 6.4 GHz 800 MHz 1 MB
P4 530
3.00 GHz 6.0 GHz 800 MHz 1 MB
P4 520
2.80 GHz 5.6 GHz 800 MHz 1 MB
ALU Speed (Core speed x2)
Pentium 4 Processor
128-bit
Integer
FPU
8-K
L1
Data
Cache
L2
Adv..
Transfer
Cache
FSB
I/F
Rapid Exe. Eng.
Branch
Prediction
CPU
ALUs
16-K Execution
Trace Cache
Out-of-Order
Core
Core speed
FSB speed (max. data transfer rate)
1-MB
L2