IBM 86884RX Installation Guide - Page 115

Choosing a Linux distribution, Byte order

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Keep these comparisons in mind while programming or porting applications to any 64-bit operating system, not only Linux. It is easy to assume that every data type is the same size, and that's why the LP Data Model standard was created. Note: The LP64 Data Model example discussed in this redbook is not the only 64-bit Data Model defined by The Open Group. There are other models, such as LP64, ILP64, or LLP64 for 64-bit and ILP32, or LP32 for 32-bit. For more information about the Data Models defined by The Open Group and also about their standardization activities, go to: http://www.opengroup.org Byte order The IA-64 kernel of Linux also uses standard byte order at a byte level. The native byte order is little-endian, while big-endian processes are still possible. All Intel processors are little-endian based. That means that the bytes at lower addresses have lower significance given a 16-bit or 32-bit word (the word is stored "little-end-first"). In big-endian architectures, the bytes addresses have higher significance (the word is stored "big-end-first"). The IA-64 Linux kernel uses little-endian by default, but allows for the possibility of using big-endian byte order. 4.3.3 Choosing a Linux distribution Unlike other operating systems, when we talk about Linux, we aren't talking about one company, one version or one distributor. Linux is the kernel, the base of the system, and there are many companies that develop Linux distributions built around the kernel. In this section, we discuss the major Linux distributors that work with IBM, and their different products available for Itanium 2 platform: Red Hat and UnitedLinux. Note: The IBM Linux support page is http://www.pc.ibm.com/qtechinfo/MIGR-48NT8D.html Here, you can find information about the Linux distributions supported by IBM, and documents, information, and drivers for IBM products. Note: Debian Linux is also available for Itanium 2 platforms, but we will not discuss this Linux distribution because it is not supported by IBM. Chapter 4. Installation 101

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Chapter 4. Installation
101
Keep these comparisons in mind while programming or porting applications to
any 64-bit operating system, not only Linux. It is easy to assume that every data
type is the same size, and that’s why the LP Data Model standard was created.
Byte order
The IA-64 kernel of Linux also uses standard byte order at a byte level. The
native byte order is little-endian, while big-endian processes are still possible.
All Intel processors are little-endian based. That means that the bytes at lower
addresses have lower significance given a 16-bit or 32-bit word (the word is
stored “little-end-first”). In big-endian architectures, the bytes addresses have
higher significance (the word is stored “big-end-first”). The IA-64 Linux kernel
uses little-endian by default, but allows for the possibility of using big-endian byte
order.
4.3.3
Choosing a Linux distribution
Unlike other operating systems, when we talk about Linux, we aren’t talking
about one company, one version or one distributor. Linux is the kernel, the base
of the system, and there are many companies that develop Linux distributions
built around the kernel.
In this section, we discuss the major Linux distributors that work with IBM, and
their different products available for Itanium 2 platform: Red Hat and UnitedLinux.
Note:
The IBM Linux support page is
Here, you can find information about the Linux distributions supported by IBM,
and documents, information, and drivers for IBM products.
Note:
The LP64 Data Model example discussed in this redbook is not the only
64-bit Data Model defined by The Open Group. There are other models, such
as LP64, ILP64, or LLP64 for 64-bit and ILP32, or LP32 for 32-bit. For more
information about the Data Models defined by The Open Group and also
about their standardization activities, go to:
Note:
Debian Linux is also available for Itanium 2 platforms, but we will not
discuss this Linux distribution because it is not supported by IBM.