| Server processors can be divided into three major categories: CISC-based processors CISC (complex instruction set computer) is a processor architecture used by x86 processors such as the Xeon, Opteron, and other server and desktop processors manufactured by Intel, AMD, and other vendors. It uses variable-length instructions. RISC-based processors RISC (reduced instruction set computer) uses a smaller number of instructions than CISC to improve processor efficiency. Server processors such as the PowerPC, Power Architecture, PA-RISC family, MIPS, Alpha, and Sun SPARC are RISC based. EPIC-based processors EPIC (explicitly parallel instruction computer) groups instructions together into very long instruction words (VLIW), preloads the instructions most likely to be used next, and uses a technique called predication to run all possible code branches in parallel and discard those that are not needed, as opposed to branch prediction (used in CISC processors). Intel's Itanium server processors are EPIC based.
| Sun SPARC processors and other unique features of the Sun SPARC server platform are discussed in detail in Chapter 19, "Sun Microsystems Servers." |
If you are planning to purchase a preconfigured server, you can choose from products in any of the listed categories. A bit less than half of the servers on the market fall into the "Wintel" (Intel/Intel-compatible hardware running Windows) category. Many users prefer other server platforms. Which category should you choose? Here are some considerations: Lowest initial cost x86-based servers, because they closely resemble x86 desktop computers in general design (and often use the same components), are the least expensive to purchase and to customize. Scalability If you need one to eight processors in a single server, any processor category can foot the bill. However, if you need a larger number of processors, you should consider a server based on RISC or EPIC technologies. Operating system support The server operating system you prefer will have a major influence on your choice of server processor. If you prefer Linux, you can choose a platform based on virtually any current or recent server processor. However, if you prefer a different server operating system, your choices are more limited. With x86 processors, you can choose from various versions of Windows 2000 Server or Windows Server 2003, popular Linux server and enterprise-level distributions, and Sun Solaris. Itanium processors can run 64-bit versions of Windows Server 2003 and Linux. Sun SPARC processors can run Linux or Solaris. PowerPC servers from Apple can run MacOS X or Linux, while PowerPC and Power architecture servers from IBM can run Linux or AIX 5L, a proprietary version of UNIX. Hewlett-Packard PA-RISCbased Hewlett-Packard 9000 series servers use HP-UX, a proprietary version of UNIX. Hewlett-Packard AlphaServers run OpenVMS, Tru64 UNIX, or Linux.
If you are planning to "roll your own" server from motherboards and other off-the-shelf components, you can choose from processors made by Intel (Itanium 2, Xeon, Pentium D, or Pentium 4) or by AMD (Opteron). If you decide to build your own server, you will be responsible for configuring and supporting it. Thus, the biggest emphasis in this chapter is on helping you understand the features of these and earlier server-compatible x86 and Itanium processors, how they differ from each other, and the tasks each is most suited for. This chapter also discusses the features of current RISC processors on the market from vendors other than Sun (whose products are covered in Chapter 19). If you prefer to purchase a preconfigured server, you should read this chapter and Chapter 19 to understand the differences between x86, EPIC, and RISC-based solutions. Whether you are working with an existing server or planning to build or purchase a new server, the details in these chapters will help you select, configure, and troubleshoot your system. |
