IBM 88554RU Installation Guide - Page 54

2.1 Migrating to a 64-bit platform With the addition of 64-bit computing to the xSeries platform you can now run large scale, mission-critical applications with the x455. The Itanium 2 processor is suitable for the next generation of high-end applications that will take advantage of its performance benefits particularly with regards to its flat memory addressable space, with a theoretical addressable memory limit of 16 EB (Exabytes). Migrating existing 32-bit applications can be a time-consuming and complex process particularly for large-scale mission-critical applications. It is also acknowledged that some applications will never need the power that 64-bit processing offers. To assist with this transition and offer backwards compatibility, the Itanium 2 offers support for IA-32 applications. In addition, Microsoft has introduced an IA-32 Execution Layer software driver to further enhance 32-bit support on Windows Server 2003. The driver works by translating IA-32 code into native Itanium architecture code before it is executed. It is available from: http://www.microsoft.com/windowsserver2003/64bit/ipf/ia32el.mspx A similar driver for Linux is also planned. To fully take advantage of 64-bit computing, it is important that your existing 32-bit applications are re-written and/or recompiled correctly. Using the 32-bit compatibility mode of the Itanium 2 or simply recompiling will not yield the potential benefits. In some cases it will even lead to poorer performance. 32-bit binaries (that is, those that run on Pentium and Xeon processor-based systems) should execute on Itanium 2 without modification. In fact, both 32-bit and 64-bit binaries can run simultaneously on the same processor. This allows a system that is only partially converted to 64 bits to run on the x455. However, unless the applications are recompiled, 32-bit applications will run slower on the Itanium 2 because of the emulation overhead and an inability to take advantage of all the benefits the 64-bit platform offers. The advantages that 64-bit offers over 32-bit are realized most for applications that can take advantage of its large addressable flat memory, ability to execute instructions in parallel, and raw computational ability particularly for applications that use floating point calculations. Before migrating, you need to consider many factors. Below are some of these considerations: Does your current operating system support 64-bit hardware? 40 IBM xSeries 455 Planning and Installation Guide Eserver