97 lines
4.8 KiB
Plaintext
97 lines
4.8 KiB
Plaintext
<!--
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$FreeBSD$
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-->
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<sect1 id="proc">
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<title>Supported Processors and Motherboards</title>
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<para>&os;/i386 runs on a wide variety of <quote>IBM PC
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compatible</quote> machines. Due to the wide range of hardware
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available for this architecture, it is impossible to exhaustively
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list all combinations of equipment supported by &os;.
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Nevertheless, some general guidelines are presented here.</para>
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<para>Almost all i386-compatible processors with a floating point unit
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are supported. All
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Intel processors beginning with the 80486 are supported, including
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the 80486, Pentium, Pentium Pro, Pentium II, Pentium III,
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Pentium 4, and variants thereof, such as the Xeon and Celeron
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processors. All i386-compatible AMD
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processors are also supported, including the Am486, Am5x86, K5, K6
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(and variants), Athlon (including Athlon-MP, Athlon-XP, Athlon-4,
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and Athlon Thunderbird), and Duron processors. The AMD
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Élan SC520 embedded processor is supported. The Transmeta
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Crusoe is recognized and supported, as are i386-compatible
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processors from Cyrix and NexGen.</para>
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<para>There is a wide variety of motherboards available for this
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architecture. Motherboards using the ISA, VLB, EISA, AGP, and PCI
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expansion busses are well-supported. There is some limited
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support for the MCA (<quote>MicroChannel</quote>) expansion bus
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used in the IBM PS/2 line of PCs.</para>
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<para>Symmetric multi-processor (SMP) systems are generally
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supported by &os;, although in some cases, BIOS or motherboard
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bugs may generate some problems. Perusal of the archives of the
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&a.smp; may yield some clues.</para>
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<para>&os; will take advantage of HyperThreading (HTT) support on
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Intel CPUs that support this feature. A kernel with the
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<literal>options SMP</literal> feature enabled will
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automatically detect the additional logical processors. The
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default &os; scheduler treats the logical processors the same as
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additional physical processors; in other words, no attempt is made
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to optimize scheduling decisions given the shared resources
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between logical processors within the same CPU. Because this
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naive scheduling can result in suboptimal performance, under
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certain circumstances it may be useful to disable the logical
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processors with the
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the <varname>machdep.hlt_logical_cpus</varname> sysctl variable.
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It is also possible to halt any CPU in the idle loop with the
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<varname>machdep.hlt_cpus</varname> sysctl variable. The
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&man.smp.4; manual page has more details.</para>
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<para>&os; will take advantage of Physical Address Extensions (PAE)
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support on CPUs that support this feature. A kernel with the
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<literal>PAE</literal> feature enabled will detect memory above
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4 gigabytes and allow it to be used by the system. This feature
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places constraints on the device drivers and other features of
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&os; which may be used; consult the &man.pae.4; manpage for more
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details.</para>
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<para>&os; will generally run on i386-based laptops, albeit with
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varying levels of support for certain hardware features such as
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sound, graphics, power management, and PCCARD expansion slots.
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These features tend to vary in idiosyncratic ways between
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machines, and frequently require special-case support in &os; to
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work around hardware bugs or other oddities. When in doubt, a
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search of the archives of the &a.mobile; may be useful.</para>
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<para>Most modern laptops (as well as many desktops) use the
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Advanced Configuration and Power Management (ACPI) standard. &os;
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supports ACPI via the ACPI Component Architecture reference
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implementation from Intel, as described in the &man.acpi.4; manual
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page. The use of ACPI causes instabilities on some machines and it
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may be necessary to disable the ACPI driver, which is normally
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loaded via a kernel module. This may be accomplished by adding
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the following line to <filename>/boot/device.hints</filename>:</para>
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<programlisting>hint.acpi.0.disabled="1"</programlisting>
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<para>Users debugging ACPI-related problems may find it useful to
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disable portions of the ACPI functionality. The &man.acpi.4;
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manual page has more information on how to do this via loader
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tunables.</para>
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<para>ACPI depends on a Differentiated System Descriptor Table
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(DSDT) provided by each machine's BIOS. Some machines have bad or
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incomplete DSDTs, which prevents ACPI from functioning correctly.
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Replacement DSDTs for some machines can be found at the <ulink
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url="http://acpi.sourceforge.net/dsdt/index.php">DSDT</ulink>
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section of the <ulink
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url="http://acpi.sourceforge.net/">ACPI4Linux</ulink> project Web
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site. &os; can use these DSDTs to override the DSDT provided by
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the BIOS; see the &man.acpi.4; manual page for more
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information.</para>
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</sect1>
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