T
ECHNOLOGY
B
RIEF
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In addition, the floating point performance of Itanium processors is significantly better than that of
today’s IA-32 processors. The Itanium processor has two extended-precision and two
single-precision floating point units, capable of executing up to four extended-precision or eight
single-precision floating point operations per clock cycle.
The Itanium processor uses a high-performance architecture, Explicitly Parallel Instruction
Computing (EPIC), which is based on very long instruction word (VLIW) systems. This
architecture achieves a new level of parallelism. New parallel-processing features include:
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Hardware support for multiple parallel data streams
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Fewer memory latencies than traditional architectures
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Better anticipation of instruction streams that can be made parallel
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Support of more parallel streams
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A third level of caching
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Making data parallel before it enters the microprocessor
Because the Itanium processor has the resources to support more registers, functional units, logic,
instructions, cache, and data, it delivers increased processing power. It also links the program
compilers more closely to the processor for more efficient execution of parallel instructions and
optimized application performance. Current IA-32 processors, on the other hand, exclusively use
hardware within the processor to decide which instructions can be executed simultaneously. The
Itanium processor uses a new instruction set designed for optimal performance with the EPIC
architecture.
The Itanium processor is also capable of executing IA-32 (x86) instructions, so it accommodates
the transition from IA-32 environments to IA-64 environments. While running an IA-32
application, the processor is switched to an IA-32 mode. When the user returns to the 64-bit OS or
launches an IA-64 application, the processor is switched back to IA-64 mode. For IA-32
applications running under a 64-bit OS that supports IA-32 applications and drivers, the OS
manages the processor mode switching. While some 32-bit software is compatible with the
Itanium processor, applications achieve higher performance when they are ported to 64-bit
versions.
Itanium processors are installed in sockets on the motherboard. A new physical form factor
(Figure 2) provides four times the bandwidth of the 330-contact slot connector design used in
Pentium II Xeon and Pentium III Xeon processors.
Figure 2: The Itanium processor uses a new physical form factor.
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TC020702TB
