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2 System Board
Devices on the Processor-Local Bus
Devices on the Processor-Local Bus
The Intel Pentium Microprocessor
The Pentium processor is packaged in a pin-grid-array (PGA), and is
seated on the system board in a zero-insertion-force (ZIF) socket 7. Only
upgrades that are pin compatible with the original processor, manufactured
by Intel, are supported.
P54CS chips working at 133 and 150 MHz (along with P54C chips working at
75, 90, 100 MHz and new versions of the 120 MHz chip) require a 3.3 V
supply. A passive shorting block is sufficient to connect the regulated 3.3 V
output of the power supply directly to the Pentium processor.
P54CS chips working at 166 and 200 MHz require between 3.45 and 3.60 V.
They need an VRE voltage regulator module (VRM), in which the voltage
is actively derived from the 3.3 V, 5 V and 0 V outlets of the power supply.
P55C chips, with MMX technology, require two voltage supplies: 3.3 V for
the input and output buffers, and 2.8 V for the core logic. It requires an
active VRM that is specifically designed for use with the MMX processor.
This VRM can be identified by the inscription “2.8 V” marked on the board.
Any thermal contact material between the processor and the heat-sink must
not be removed or disturbed. The cooling needs of the processor are critical.
MMX Technology
The instruction set of the MMX processor includes 57 new instructions, four
new 64-bit data formats (depicted below) and eight new 64-bit MMX
registers. As well as the pipelined parallelism of the traditional Pentium
architecture, MMX is capable of SIMD parallelism (single-instruction/
multiple-data). Instead of combining a pair of operands to produce a single
result, each instruction is able to gang each operation over a large number of
pairs of operands, so producing a large number of results concurrently. This
type of parallelism is particularly useful when processing large vectors and
arrays of data (in graphics and audio processing, for example).
Quadword 64 bit
Packed double word 32 bit 32 bit
Packed word 16 bit 16 bit 16 bit 16 bit
Packed byte 8 bit 8 bit 8 bit 8 bit 8 bit 8 bit 8 bit 8 bit