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(Intel Architecture-64) The 64-bit architecture used in Intel's Itanium family of CPU chips. Engineered for server processing, Itanium/IA-64 was designed when millions more transistors on a chip were commonplace, which was two decades after Intel developed its first x86 CPUs. Later on, Intel also upgraded the x86 line to 64 bits (see Intel 64). See Itanium and x86.

Recompilation Required
Although applications written for x86 and HP 9000 computers run intact on IA-64 machines via translation layers (see IA 32 Execution Layer), programs have to be recompiled in order to take advantage of IA-64.

Rather than variable-length instructions as in x86 (IA-32), IA-64 uses fixed-length, four-byte instructions bundled in sets of three "long instruction words." IA-64 uses 256 registers for integer and floating point operations compared to 16 in IA-32.

IA-64 Predicts the Future
To take advantage of an advanced pipeline architecture, IA-64 employs "predication." Both sides of a branch instruction following a compare are executed in parallel. After determining which branch is correct, the results of the other are discarded. IA-64 compilers have to set up the predication; they have to interleave the instructions and add codes that tell the CPU how to execute in parallel. If predication is not set up, the CPU performs a simpler prediction, whereby it executes in parallel the side of the branch that it thinks will be the outcome, not both sides. If it guesses wrong, the parallelism is lost for those few nanoseconds.

IA-64 also supports speculative loading, which loads data into registers before the instructions actually need to process it. Intel brands this parallel architecture "Explicitly Parallel Instruction Computing" (EPIC), and sometimes refers to the IA-64 architecture as EPIC; thus, IA-64 and EPIC are synonymous.
References in periodicals archive ?
0 based Intel IA-64 system, will be available at the 2000 ANSYS Conference and Exhibition August 28-30 in Pittsburgh Pa.
TurboLinux, the first company to make an IA-64 Linux distribution available to developers last March, recently announced the fifth upgrade of its TurboLinux for IA-64 developer's release operating system.
Rational is committed to providing a complete life-cycle solution on Linux, Monterey and Windows 2000 to help customers rapidly embrace Intel's IA-64 architecture.
Thanks to the tremendous efforts of the Trillian team members thus far, the kernel for IA-64 Linux is rapidly approaching full functionality," said Sridhar Chilukuri, director of business development for VA Linux Systems.
SGI previously announced its plans to deliver a family of IA-64 servers based on the Merced architecture designed for performance, high availability and serviceability.
30 /PRNewswire/ -- SCO (Nasdaq: SCOC) today reinforced its leadership position in developing a 64-bit UNIX system for the IA-64 architecture by shipping an early release of its UnixWare operating system for IA-64, along with a development environment, to selected Merced partners.
The Intel 64 Fund is a quarter billion dollar equity fund that invests in emerging technologies for next-generation servers and workstations utilizing Intel's IA-64 architecture.
Ron Curry, director of marketing, IA-64 processor division, said that Intel anticipated that existing applications "will run about the speed of the volume IA-32 chips shipping at the time.
Users of Softimage's 3-D products will clearly benefit from IA-64 processor performance," said Anand Chandrasekher, general manager of the workstation products division at Intel.
There is not likely to any further news on IA-64 availability.
Santa Cruz Operation Inc is cruising along as it waits for the opportunity which it hopes will be provided by the arrival of Intel Corp's IA-64 architecture and the IBM Corp AIX-based Montery64 operating system which it will sell on IA-64 systems as its next-generation Unix.
Also known as N4000, the mid-range multiprocessor marks the beginning of HP's migration to the IA-64 architecture it co-designed with Intel.