2 IA-32 support
In order to support IA-32, the Itanium can switch into 32-bit mode with special jump escape instructions. The IA-32 instructions have been mapped to the Itanium's functional units. However, since the Itanium is built primarily for speed of its EPIC-style instructions, and because it has no out-of-order execution capabilities, IA-32 code executes at a severe performance penalty compared to either the IA-64 mode, or its Pentium line of processors. For example, the Itanium functional units do not automatically generate integer flags as a side effect of ordinary ALU computation, and does not intrinsically support multiple outstanding unaligned memory loads. There have been reports that Intel is seeking a software emulation based solution (much like TransmetaTransmeta is a US-based corporation that makes energy efficient x86 microprocessors. To date, it has produced two x86 compatible CPU architectures: the Crusoe and Efficeon processors. These CPUs have appeared in ultra-portable Laptops, Blade servers, Tabl did) for executing IA-32 code in future versions of Itanium to replace the current hardware solution.
3 Competitors
Although other 64-bit architectures have existed for a long time, most ( MIPSMIPS for ''M''icroprocessor without i''nterlocked p''ipeline s''tages is a RISC microprocessor architecture developed by MIPS Computer Systems Inc. MIPS designs are used in SGI's computer product line, and have found broad application in embedded systems,, AlphaAXP" redirects here. AXP also is the stock symbol for American Express. The DEC Alpha also known as the Alpha AXP is a 64-bit RISC microprocessor originally developed and fabricated by Digital Equipment Corp. DEC), which used it in its own line of worksta, PA-RISCPA-RISC is a microprocessor architecture developed by Hewlett-Packard's Systems & VLSI Technology Operation''. As the name implies, it is an implementation using a RISC design, where the PA stands for P recision A rchitecture''. The design is also referre) have faded from the marketplace. Itanium's remaining competition for the 64-bit server and workstation market appear to be the newcomer AMDFor other possible meanings of AMD see AMD (disambiguation Advanced Micro Devices, Inc. AMD ( NYSE:AMD) is a manufacturer of integrated circuits based in Sunnyvale, California. It is the second-largest supplier of x86 compatible processors, and a leading with its AMD64The AMD64 is a 64-bit processor architecture invented by AMD. It is a superset of the x86 architecture, which it natively supports. Architecture overview TODO write about the AMD64 architecture. New instructions, capabilities, register sizes, etc. NX Bit architecture, and the entrenched rivals: IBM's POWER architecture, and Sun's UltraSparc architecture. Apple may also challenge Intel with its XServe product line based on the IBM PowerPC architecture.
Intel has so far only marketed the Itanium in the high-end work station, server and super-computer space.
In response to favourable industry reaction to the AMD64, Intel has plans for future versions of the Xeon to support its EM64T extensions to IA-32, which are largely instruction-set compatible with AMD64.
4 See also
5 External links
Computer terminology
Computer architecture
Microprocessors
