CONFIG_SMP
This enables support for systems with more than one CPU. If you have
a system with only one CPU, like most personal computers, say N. If
you have a system with more than one CPU, say Y.
If you say N here, the kernel will run on single and multiprocessor
machines, but will use only one CPU of a multiprocessor machine. If
you say Y here, the kernel will run on many, but not all,
singleprocessor machines. On a singleprocessor machine, the kernel
will run faster if you say N here.
Note that if you say Y here and choose architecture "586" or
"Pentium" under "Processor family", the kernel will not work on 486
architectures. Similarly, multiprocessor kernels for the "PPro"
architecture may not work on all Pentium based boards.
People using multiprocessor machines who say Y here should also say
Y to "Enhanced Real Time Clock Support", below. The "Advanced Power
Management" code will be disabled if you say Y here.
See also the <file:Documentation/smp.tex>,
<file:Documentation/smp.txt>, <file:Documentation/i386/IO-APIC.txt>,
<file:Documentation/nmi_watchdog.txt> and the SMP-HOWTO available at
<http://www.linuxdoc.org/docs.html#howto>.
If you don't know what to do here, say N.
CONFIG_PREEMPT
This option reduces the latency of the kernel when reacting to
real-time or interactive events by allowing a low priority process to
be preempted even if it is in kernel mode executing a system call.
This allows applications to run more reliably even when the system is
under load.
Say Y here if you are building a kernel for a desktop, embedded
or real-time system. Say N if you are unsure.
CONFIG_X86
This is Linux's home port. Linux was originally native to the Intel
386, and runs on all the later x86 processors including the Intel
486, 586, Pentiums, and various instruction-set-compatible chips by
AMD, Cyrix, and others.
CONFIG_X86_NUMAQ
This option is used for getting Linux to run on a (IBM/Sequent) NUMA
multiquad box. This changes the way that processors are bootstrapped,
and uses Clustered Logical APIC addressing mode instead of Flat Logical.
You will need a new lynxer.elf file to flash your firmware with - send
email to Martin.Bligh@us.ibm.com
CONFIG_X86_UP_IOAPIC
An IO-APIC (I/O Advanced Programmable Interrupt Controller) is an
SMP-capable replacement for PC-style interrupt controllers. Most
SMP systems and a small number of uniprocessor systems have one.
If you have a single-CPU system with an IO-APIC, you can say Y here
to use it. If you say Y here even though your machine doesn't have
an IO-APIC, then the kernel will still run with no slowdown at all.
If you have a system with several CPUs, you do not need to say Y
here: the IO-APIC will be used automatically.
CONFIG_X86_UP_APIC
A local APIC (Advanced Programmable Interrupt Controller) is an
integrated interrupt controller in the CPU. If you have a single-CPU
system which has a processor with a local APIC, you can say Y here to
enable and use it. If you say Y here even though your machine doesn't
have a local APIC, then the kernel will still run with no slowdown at
all. The local APIC supports CPU-generated self-interrupts (timer,
performance counters), and the NMI watchdog which detects hard lockups.
If you have a system with several CPUs, you do not need to say Y
here: the local APIC will be used automatically.
CONFIG_MATH_EMULATION
Linux can emulate a math coprocessor (used for floating point
operations) if you don't have one. 486DX and Pentium processors have
a math coprocessor built in, 486SX and 386 do not, unless you added
a 487DX or 387, respectively. (The messages during boot time can
give you some hints here ["man dmesg"].) Everyone needs either a
coprocessor or this emulation.
If you don't have a math coprocessor, you need to say Y here; if you
say Y here even though you have a coprocessor, the coprocessor will
be used nevertheless. (This behavior can be changed with the kernel
command line option "no387", which comes handy if your coprocessor
is broken. Try "man bootparam" or see the documentation of your boot
loader (lilo or loadlin) about how to pass options to the kernel at
boot time.) This means that it is a good idea to say Y here if you
intend to use this kernel on different machines.
More information about the internals of the Linux math coprocessor
emulation can be found in <file:arch/i386/math-emu/README>.
If you are not sure, say Y; apart from resulting in a 66 KB bigger
kernel, it won't hurt.
CONFIG_NOHIGHMEM
Linux can use up to 64 Gigabytes of physical memory on x86 systems.
However, the address space of 32-bit x86 processors is only 4
Gigabytes large. That means that, if you have a large amount of
physical memory, not all of it can be "permanently mapped" by the
kernel. The physical memory that's not permanently mapped is called
"high memory".
If you are compiling a kernel which will never run on a machine with
more than 1 Gigabyte total physical RAM, answer "off" here (default
choice and suitable for most users). This will result in a "3GB/1GB"
split: 3GB are mapped so that each process sees a 3GB virtual memory
space and the remaining part of the 4GB virtual memory space is used
by the kernel to permanently map as much physical memory as
possible.
If the machine has between 1 and 4 Gigabytes physical RAM, then
answer "4GB" here.
If more than 4 Gigabytes is used then answer "64GB" here. This
selection turns Intel PAE (Physical Address Extension) mode on.
PAE implements 3-level paging on IA32 processors. PAE is fully
supported by Linux, PAE mode is implemented on all recent Intel
processors (Pentium Pro and better). NOTE: If you say "64GB" here,
then the kernel will not boot on CPUs that don't support PAE!
The actual amount of total physical memory will either be
auto detected or can be forced by using a kernel command line option
such as "mem=256M". (Try "man bootparam" or see the documentation of
your boot loader (lilo or loadlin) about how to pass options to the
kernel at boot time.)
If unsure, say "off".
CONFIG_HIGHPTE
The VM uses one page table entry for each page of physical memory.
For systems with a lot of RAM, this can be wasteful of precious
low memory. Setting this option will put user-space page table
entries in high memory.
CONFIG_HIGHMEM4G
Select this if you have a 32-bit processor and between 1 and 4
gigabytes of physical RAM.
CONFIG_HIGHMEM64G
Select this if you have a 32-bit processor and more than 4
gigabytes of physical RAM.
CONFIG_IDE
If you say Y here, your kernel will be able to manage low cost mass
storage units such as ATA/(E)IDE and ATAPI units. The most common
cases are IDE hard drives and ATAPI CD-ROM drives.
If your system is pure SCSI and doesn't use these interfaces, you
can say N here.
Integrated Disk Electronics (IDE aka ATA-1) is a connecting standard
for mass storage units such as hard disks. It was designed by
Western Digital and Compaq Computer in 1984. It was then named
ST506. Quite a number of disks use the IDE interface.
AT Attachment (ATA) is the superset of the IDE specifications.
ST506 was also called ATA-1.
Fast-IDE is ATA-2 (also named Fast ATA), Enhanced IDE (EIDE) is
ATA-3. It provides support for larger disks (up to 8.4GB by means of
the LBA standard), more disks (4 instead of 2) and for other mass
storage units such as tapes and cdrom. UDMA/33 (aka UltraDMA/33) is
ATA-4 and provides faster (and more CPU friendly) transfer modes
than previous PIO (Programmed processor Input/Output) from previous
ATA/IDE standards by means of fast DMA controllers.
ATA Packet Interface (ATAPI) is a protocol used by EIDE tape and
CD-ROM drives, similar in many respects to the SCSI protocol.
SMART IDE (Self Monitoring, Analysis and Reporting Technology) was
designed in order to prevent data corruption and disk crash by
detecting pre hardware failure conditions (heat, access time, and
the like...). Disks built since June 1995 may follow this standard.
The kernel itself don't manage this; however there are quite a
number of user programs such as smart that can query the status of
SMART parameters disk.
If you want to compile this driver as a module ( = code which can be
inserted in and removed from the running kernel whenever you want),
say M here and read <file:Documentation/modules.txt>. The module
will be called ide.o.
For further information, please read <file:Documentation/ide.txt>.
If unsure, say Y.
CONFIG_ISA
Find out whether you have ISA slots on your motherboard. ISA is the
name of a bus system, i.e. the way the CPU talks to the other stuff
inside your box. Other bus systems are PCI, EISA, MicroChannel
(MCA) or VESA. ISA is an older system, now being displaced by PCI;
newer boards don't support it. If you have ISA, say Y, otherwise N.
CONFIG_PCI
Find out whether you have a PCI motherboard. PCI is the name of a
bus system, i.e. the way the CPU talks to the other stuff inside
your box. Other bus systems are ISA, EISA, MicroChannel (MCA) or
VESA. If you have PCI, say Y, otherwise N.
The PCI-HOWTO, available from
<http://www.linuxdoc.org/docs.html#howto>, contains valuable
information about which PCI hardware does work under Linux and which
doesn't.
CONFIG_PCI_GOBIOS
On PCI systems, the BIOS can be used to detect the PCI devices and
determine their configuration. However, some old PCI motherboards
have BIOS bugs and may crash if this is done. Also, some embedded
PCI-based systems don't have any BIOS at all. Linux can also try to
detect the PCI hardware directly without using the BIOS.
With this option, you can specify how Linux should detect the PCI
devices. If you choose "BIOS", the BIOS will be used, if you choose
"Direct", the BIOS won't be used, and if you choose "Any", the
kernel will try the direct access method and falls back to the BIOS
if that doesn't work. If unsure, go with the default, which is
"Any".
CONFIG_HOTPLUG_PCI
Say Y here if you have a motherboard with a PCI Hotplug controller.
This allows you to add and remove PCI cards while the machine is
powered up and running. The file system pcihpfs must be mounted
in order to interact with any PCI Hotplug controllers.
This code is also available as a module ( = code which can be
inserted in and removed from the running kernel whenever you want).
The module will be called pci_hotplug.o. If you want to compile it
as a module, say M here and read <file:Documentation/modules.txt>.
When in doubt, say N.
CONFIG_MCA
MicroChannel Architecture is found in some IBM PS/2 machines and
laptops. It is a bus system similar to PCI or ISA. See
<file:Documentation/mca.txt> (and especially the web page given
there) before attempting to build an MCA bus kernel.
CONFIG_EISA
The Extended Industry Standard Architecture (EISA) bus was
developed as an open alternative to the IBM MicroChannel bus.
The EISA bus provided some of the features of the IBM MicroChannel
bus while maintaining backward compatibility with cards made for
the older ISA bus. The EISA bus saw limited use between 1988 and
1995 when it was made obsolete by the PCI bus.
Say Y here if you are building a kernel for an EISA-based machine.
Otherwise, say N.
CONFIG_VISWS
The SGI Visual Workstation series is an IA32-based workstation
based on SGI systems chips with some legacy PC hardware attached.
Say Y here to create a kernel to run on the SGI 320 or 540.
A kernel compiled for the Visual Workstation will not run on other
PC boards and vice versa.
See <file:Documentation/sgi-visws.txt> for more.
CONFIG_HOTPLUG
Say Y here if you want to plug devices into your computer while
the system is running, and be able to use them quickly. In many
cases, the devices can likewise be unplugged at any time too.
One well known example of this is PCMCIA- or PC-cards, credit-card
size devices such as network cards, modems or hard drives which are
plugged into slots found on all modern laptop computers. Another
example, used on modern desktops as well as laptops, is USB.
Enable HOTPLUG and KMOD, and build a modular kernel. Get agent
software (at <http://linux-hotplug.sourceforge.net/>) and install it.
Then your kernel will automatically call out to a user mode "policy
agent" (/sbin/hotplug) to load modules and set up software needed
to use devices as you hotplug them.
CONFIG_PCMCIA
Say Y here if you want to attach PCMCIA- or PC-cards to your Linux
computer. These are credit-card size devices such as network cards,
modems or hard drives often used with laptops computers. There are
actually two varieties of these cards: the older 16 bit PCMCIA cards
and the newer 32 bit CardBus cards. If you want to use CardBus
cards, you need to say Y here and also to "CardBus support" below.
To use your PC-cards, you will need supporting software from David
Hinds' pcmcia-cs package (see the file <file:Documentation/Changes>
for location). Please also read the PCMCIA-HOWTO, available from
<http://www.linuxdoc.org/docs.html#howto>.
This driver is also available as a module ( = code which can be
inserted in and removed from the running kernel whenever you want).
When compiled this way, there will be modules called pcmcia_core.o
and ds.o. If you want to compile it as a module, say M here and
read <file:Documentation/modules.txt>.
CONFIG_KCORE_ELF
If you enabled support for /proc file system then the file
/proc/kcore will contain the kernel core image. This can be used
in gdb:
$ cd /usr/src/linux ; gdb vmlinux /proc/kcore
You have two choices here: ELF and A.OUT. Selecting ELF will make
/proc/kcore appear in ELF core format as defined by the Executable
and Linking Format specification. Selecting A.OUT will choose the
old "a.out" format which may be necessary for some old versions
of binutils or on some architectures.
This is especially useful if you have compiled the kernel with the
"-g" option to preserve debugging information. It is mainly used
for examining kernel data structures on the live kernel so if you
don't understand what this means or are not a kernel hacker, just
leave it at its default value ELF.
CONFIG_KCORE_AOUT
Not necessary unless you're using a very out-of-date binutils
version. You probably want KCORE_ELF.
CONFIG_BINFMT_ELF
ELF (Executable and Linkable Format) is a format for libraries and
executables used across different architectures and operating
systems. Saying Y here will enable your kernel to run ELF binaries
and enlarge it by about 13 KB. ELF support under Linux has now all
but replaced the traditional Linux a.out formats (QMAGIC and ZMAGIC)
because it is portable (this does *not* mean that you will be able
to run executables from different architectures or operating systems
however) and makes building run-time libraries very easy. Many new
executables are distributed solely in ELF format. You definitely
want to say Y here.
Information about ELF is contained in the ELF HOWTO available from
<http://www.linuxdoc.org/docs.html#howto>.
If you find that after upgrading from Linux kernel 1.2 and saying Y
here, you still can't run any ELF binaries (they just crash), then
you'll have to install the newest ELF runtime libraries, including
ld.so (check the file <file:Documentation/Changes> for location and
latest version).
If you want to compile this as a module ( = code which can be
inserted in and removed from the running kernel whenever you want),
say M here and read <file:Documentation/modules.txt>. The module
will be called binfmt_elf.o. Saying M or N here is dangerous because
some crucial programs on your system might be in ELF format.
CONFIG_BINFMT_AOUT
A.out (Assembler.OUTput) is a set of formats for libraries and
executables used in the earliest versions of UNIX. Linux used the
a.out formats QMAGIC and ZMAGIC until they were replaced with the
ELF format.
As more and more programs are converted to ELF, the use for a.out
will gradually diminish. If you disable this option it will reduce
your kernel by one page. This is not much and by itself does not
warrant removing support. However its removal is a good idea if you
wish to ensure that absolutely none of your programs will use this
older executable format. If you don't know what to answer at this
point then answer Y. If someone told you "You need a kernel with
QMAGIC support" then you'll have to say Y here. You may answer M to
compile a.out support as a module and later load the module when you
want to use a program or library in a.out format. The module will be
called binfmt_aout.o. Saying M or N here is dangerous though,
because some crucial programs on your system might still be in A.OUT
format.
CONFIG_BINFMT_MISC
If you say Y here, it will be possible to plug wrapper-driven binary
formats into the kernel. You will like this especially when you use
programs that need an interpreter to run like Java, Python or
Emacs-Lisp. It's also useful if you often run DOS executables under
the Linux DOS emulator DOSEMU (read the DOSEMU-HOWTO, available from
<http://www.linuxdoc.org/docs.html#howto>). Once you have
registered such a binary class with the kernel, you can start one of
those programs simply by typing in its name at a shell prompt; Linux
will automatically feed it to the correct interpreter.
You can do other nice things, too. Read the file
<file:Documentation/binfmt_misc.txt> to learn how to use this
feature, and <file:Documentation/java.txt> for information about how
to include Java support.
You must say Y to "/proc file system support" (CONFIG_PROC_FS) to
use this part of the kernel.
You may say M here for module support and later load the module when
you have use for it; the module is called binfmt_misc.o. If you
don't know what to answer at this point, say Y.
CONFIG_M386
This is the processor type of your CPU. This information is used for
optimizing purposes. In order to compile a kernel that can run on
all x86 CPU types (albeit not optimally fast), you can specify
"386" here.
The kernel will not necessarily run on earlier architectures than
the one you have chosen, e.g. a Pentium optimized kernel will run on
a PPro, but not necessarily on a i486.
Here are the settings recommended for greatest speed:
- "386" for the AMD/Cyrix/Intel 386DX/DXL/SL/SLC/SX, Cyrix/TI
486DLC/DLC2, UMC 486SX-S and NexGen Nx586. Only "386" kernels
will run on a 386 class machine.
- "486" for the AMD/Cyrix/IBM/Intel 486DX/DX2/DX4 or
SL/SLC/SLC2/SLC3/SX/SX2 and UMC U5D or U5S.
- "586" for generic Pentium CPUs lacking the TSC
(time stamp counter) register.
- "Pentium-Classic" for the Intel Pentium.
- "Pentium-MMX" for the Intel Pentium MMX.
- "Pentium-Pro" for the Intel Pentium Pro/Celeron/Pentium II.
- "Pentium-III" for the Intel Pentium III
and Celerons based on the Coppermine core.
- "Pentium-4" for the Intel Pentium 4.
- "K6" for the AMD K6, K6-II and K6-III (aka K6-3D).
- "Athlon" for the AMD K7 family (Athlon/Duron/Thunderbird).
- "Crusoe" for the Transmeta Crusoe series.
- "Winchip-C6" for original IDT Winchip.
- "Winchip-2" for IDT Winchip 2.
- "Winchip-2A" for IDT Winchips with 3dNow! capabilities.
- "CyrixIII" for VIA Cyrix III or VIA C3.
If you don't know what to do, choose "386".
CONFIG_M486
Select this for a x486 processor, ether Intel or one of the
compatible processors from AMD, Cyrix, IBM, or Intel. Includes DX,
DX2, and DX4 variants; also SL/SLC/SLC2/SLC3/SX/SX2 and UMC U5D or
U5S.
CONFIG_M586
Select this for an x586 or x686 processor such as the AMD K5, the
Intel 5x86 or 6x86, or the Intel 6x86MX. This choice does not
assume the RDTSC (Read Time Stamp Counter) instruction.
CONFIG_M586TSC
Select this for a Pentium Classic processor with the RDTSC (Read
Time Stamp Counter) instruction for benchmarking.
CONFIG_M586MMX
Select this for a Pentium with the MMX graphics/multimedia
extended instructions.
CONFIG_M686
Select this for a Pro/Celeron/Pentium II. This enables the use of
Pentium Pro extended instructions, and disables the init-time guard
against the f00f bug found in earlier Pentiums.
CONFIG_MPENTIUMIII
Select this for Intel chips based on the Pentium-III and
Celeron-Coppermine core. Enables use of some extended prefetch
instructions, in addition to the Pentium II extensions.
CONFIG_MPENTIUM4
Select this for Intel Pentium 4 chips. Presently these are
treated almost like Pentium IIIs, but with a different cache
shift.
CONFIG_MCRUSOE
Select this for Transmeta Crusoe processor. Treats the processor
like a 586 with TSC, and sets some GCC optimization flags (like a
Pentium Pro with no alignment requirements).
CONFIG_MK6
Select this for an AMD K6-family processor. Enables use of
some extended instructions, and passes appropriate optimization
flags to GCC.
CONFIG_MK7
Select this for an AMD Athlon K7-family processor. Enables use of
some extended instructions, and passes appropriate optimization
flags to GCC.
CONFIG_MCYRIXIII
Select this for a Cyrix III or C3 chip. Presently Linux and GCC
treat this chip as a generic 586. Whilst the CPU is 686 class,
it lacks the cmov extension which gcc assumes is present when
generating 686 code.
CONFIG_MWINCHIPC6
Select this for a IDT Winchip C6 chip. Linux and GCC
treat this chip as a 586TSC with some extended instructions
and alignment requirements.
CONFIG_MWINCHIP2
Select this for a IDT Winchip-2. Linux and GCC
treat this chip as a 586TSC with some extended instructions
and alignment requirements.
CONFIG_MWINCHIP3D
Select this for a IDT Winchip-2A or 3. Linux and GCC
treat this chip as a 586TSC with some extended instructions
and alignment reqirements. Development kernels also enable
out of order memory stores for this CPU, which can increase
performance of some operations.
CONFIG_VGA_CONSOLE
Saying Y here will allow you to use Linux in text mode through a
display that complies with the generic VGA standard. Virtually
everyone wants that.
The program SVGATextMode can be used to utilize SVGA video cards to
their full potential in text mode. Download it from
<ftp://ibiblio.org/pub/Linux/utils/console/>.
Say Y.
CONFIG_VIDEO_SELECT
This enables support for text mode selection on kernel startup. If
you want to take advantage of some high-resolution text mode your
card's BIOS offers, but the traditional Linux utilities like
SVGATextMode don't, you can say Y here and set the mode using the
"vga=" option from your boot loader (lilo or loadlin) or set
"vga=ask" which brings up a video mode menu on kernel startup. (Try
"man bootparam" or see the documentation of your boot loader about
how to pass options to the kernel.)
Read the file <file:Documentation/svga.txt> for more information
about the Video mode selection support. If unsure, say N.
CONFIG_MDA_CONSOLE
Say Y here if you have an old MDA or monochrome Hercules graphics
adapter in your system acting as a second head ( = video card). You
will then be able to use two monitors with your Linux system. Do not
say Y here if your MDA card is the primary card in your system; the
normal VGA driver will handle it.
This driver is also available as a module ( = code which can be
inserted and removed from the running kernel whenever you want).
The module will be called mdacon.o. If you want to compile it as
a module, say M here and read <file:Documentation/modules.txt>.
If unsure, say N.
CONFIG_SCSI
If you want to use a SCSI hard disk, SCSI tape drive, SCSI CD-ROM or
any other SCSI device under Linux, say Y and make sure that you know
the name of your SCSI host adapter (the card inside your computer
that "speaks" the SCSI protocol, also called SCSI controller),
because you will be asked for it.
You also need to say Y here if you want support for the parallel
port version of the 100 MB IOMEGA ZIP drive.
This driver is also available as a module ( = code which can be
inserted in and removed from the running kernel whenever you want).
The module will be called scsi_mod.o. If you want to compile it as
a module, say M here and read <file:Documentation/modules.txt> and
<file:Documentation/scsi.txt>. However, do not compile this as a
module if your root file system (the one containing the directory /)
is located on a SCSI device.
CONFIG_NETDEVICES
You can say N here if you don't intend to connect your Linux box to
any other computer at all or if all your connections will be over a
telephone line with a modem either via UUCP (UUCP is a protocol to
forward mail and news between unix hosts over telephone lines; read
the UUCP-HOWTO, available from
<http://www.linuxdoc.org/docs.html#howto>) or dialing up a shell
account or a BBS, even using term (term is a program which gives you
almost full Internet connectivity if you have a regular dial up
shell account on some Internet connected Unix computer. Read
<http://www.bart.nl/~patrickr/term-howto/Term-HOWTO.html>).
You'll have to say Y if your computer contains a network card that
you want to use under Linux (make sure you know its name because you
will be asked for it and read the Ethernet-HOWTO (especially if you
plan to use more than one network card under Linux)) or if you want
to use SLIP (Serial Line Internet Protocol is the protocol used to
send Internet traffic over telephone lines or null modem cables) or
CSLIP (compressed SLIP) or PPP (Point to Point Protocol, a better
and newer replacement for SLIP) or PLIP (Parallel Line Internet
Protocol is mainly used to create a mini network by connecting the
parallel ports of two local machines) or AX.25/KISS (protocol for
sending Internet traffic over amateur radio links).
Make sure to read the NET-3-HOWTO. Eventually, you will have to read
Olaf Kirch's excellent and free book "Network Administrator's
Guide", to be found in <http://www.linuxdoc.org/docs.html#guide>. If
unsure, say Y.
CONFIG_CD_NO_IDESCSI
If you have a CD-ROM drive that is neither SCSI nor IDE/ATAPI, say Y
here, otherwise N. Read the CD-ROM-HOWTO, available from
<http://www.linuxdoc.org/docs.html#howto>.
Note that the answer to this question doesn't directly affect the
kernel: saying N will just cause the configurator to skip all
the questions about these CD-ROM drives. If you are unsure what you
have, say Y and find out whether you have one of the following
drives.
For each of these drivers, a file Documentation/cdrom/{driver_name}
exists. Especially in cases where you do not know exactly which kind
of drive you have you should read there. Most of these drivers use a
file drivers/cdrom/{driver_name}.h where you can define your
interface parameters and switch some internal goodies.
All these CD-ROM drivers are also usable as a module ( = code which
can be inserted in and removed from the running kernel whenever you
want). If you want to compile them as module, say M instead of Y and
read <file:Documentation/modules.txt>.
If you want to use any of these CD-ROM drivers, you also have to
answer Y or M to "ISO 9660 CD-ROM file system support" below (this
answer will get "defaulted" for you if you enable any of the Linux
CD-ROM drivers).
CONFIG_MTRR
On Intel P6 family processors (Pentium Pro, Pentium II and later)
the Memory Type Range Registers (MTRRs) may be used to control
processor access to memory ranges. This is most useful if you have
a video (VGA) card on a PCI or AGP bus. Enabling write-combining
allows bus write transfers to be combined into a larger transfer
before bursting over the PCI/AGP bus. This can increase performance
of image write operations 2.5 times or more. Saying Y here creates a
/proc/mtrr file which may be used to manipulate your processor's
MTRRs. Typically the X server should use this.
This code has a reasonably generic interface so that similar
control registers on other processors can be easily supported
as well:
The Cyrix 6x86, 6x86MX and M II processors have Address Range
Registers (ARRs) which provide a similar functionality to MTRRs. For
these, the ARRs are used to emulate the MTRRs.
The AMD K6-2 (stepping 8 and above) and K6-3 processors have two
MTRRs. The Centaur C6 (WinChip) has 8 MCRs, allowing
write-combining. All of these processors are supported by this code
and it makes sense to say Y here if you have one of them.
Saying Y here also fixes a problem with buggy SMP BIOSes which only
set the MTRRs for the boot CPU and not for the secondary CPUs. This
can lead to all sorts of problems, so it's good to say Y here.
You can safely say Y even if your machine doesn't have MTRRs, you'll
just add about 9 KB to your kernel.
See <file:Documentation/mtrr.txt> for more information.
CONFIG_PM
"Power Management" means that parts of your computer are shut
off or put into a power conserving "sleep" mode if they are not
being used. There are two competing standards for doing this: APM
and ACPI. If you want to use either one, say Y here and then also
to the requisite support below.
Power Management is most important for battery powered laptop
computers; if you have a laptop, check out the Linux Laptop home
page on the WWW at
<http://www.cs.utexas.edu/users/kharker/linux-laptop/> and the
Battery Powered Linux mini-HOWTO, available from
<http://www.linuxdoc.org/docs.html#howto>.
Note that, even if you say N here, Linux on the x86 architecture
will issue the hlt instruction if nothing is to be done, thereby
sending the processor to sleep and saving power.
CONFIG_ACPI
Advanced Configuration and Power Interface (ACPI) support for
Linux requires an ACPI compliant platform (hardware/firmware),
and assumes the presence of OS-directed configuration and power
management (OSPM) software. This option will enlarge your
kernel by about 70K.
Linux ACPI provides a robust functional replacement for several
legacy configuration and power management intefaces, including
the Plug-and-Play BIOS specification (PnP BIOS), the
MultiProcessor Specification (MPS), and the Advanced Power
Management (APM) specification. If both ACPI and APM support
are configured, whichever is loaded first shall be used.
The ACPI SourceForge project contains the latest source code,
documentation, tools, mailing list subscription, and other
information. This project is available at:
<http://sourceforge.net/projects/acpi>
Linux support for ACPI is based on Intel Corporation's ACPI
Component Architecture (ACPI CA). For more information see:
<http://developer.intel.com/technology/iapc/acpi>
ACPI is an open industry specification co-developed by Compaq,
Intel, Microsoft, Phoenix, and Toshiba. The specification is
available at:
<http://www.acpi.info>
CONFIG_APM
APM is a BIOS specification for saving power using several different
techniques. This is mostly useful for battery powered laptops with
APM compliant BIOSes. If you say Y here, the system time will be
reset after a RESUME operation, the /proc/apm device will provide
battery status information, and user-space programs will receive
notification of APM "events" (e.g. battery status change).
If you select "Y" here, you can disable actual use of the APM
BIOS by passing the "apm=off" option to the kernel at boot time.
Note that the APM support is almost completely disabled for
machines with more than one CPU.
In order to use APM, you will need supporting software. For location
and more information, read <file:Documentation/pm.txt> and the
Battery Powered Linux mini-HOWTO, available from
<http://www.linuxdoc.org/docs.html#howto>.
This driver does not spin down disk drives (see the hdparm(8)
manpage ("man 8 hdparm") for that), and it doesn't turn off
VESA-compliant "green" monitors.
This driver does not support the TI 4000M TravelMate and the ACER
486/DX4/75 because they don't have compliant BIOSes. Many "green"
desktop machines also don't have compliant BIOSes, and this driver
may cause those machines to panic during the boot phase.
Generally, if you don't have a battery in your machine, there isn't
much point in using this driver and you should say N. If you get
random kernel OOPSes or reboots that don't seem to be related to
anything, try disabling/enabling this option (or disabling/enabling
APM in your BIOS).
Some other things you should try when experiencing seemingly random,
"weird" problems:
1) make sure that you have enough swap space and that it is
enabled.
2) pass the "no-hlt" option to the kernel
3) switch on floating point emulation in the kernel and pass
the "no387" option to the kernel
4) pass the "floppy=nodma" option to the kernel
5) pass the "mem=4M" option to the kernel (thereby disabling
all but the first 4 MB of RAM)
6) make sure that the CPU is not over clocked.
7) read the sig11 FAQ at <http://www.bitwizard.nl/sig11/>
8) disable the cache from your BIOS settings
9) install a fan for the video card or exchange video RAM
10) install a better fan for the CPU
11) exchange RAM chips
12) exchange the motherboard.
To compile this driver as a module ( = code which can be inserted in
and removed from the running kernel whenever you want), say M here
and read <file:Documentation/modules.txt>. The module will be called
apm.o.
CONFIG_APM_IGNORE_USER_SUSPEND
This option will ignore USER SUSPEND requests. On machines with a
compliant APM BIOS, you want to say N. However, on the NEC Versa M
series notebooks, it is necessary to say Y because of a BIOS bug.
CONFIG_APM_DO_ENABLE
Enable APM features at boot time. From page 36 of the APM BIOS
specification: "When disabled, the APM BIOS does not automatically
power manage devices, enter the Standby State, enter the Suspend
State, or take power saving steps in response to CPU Idle calls."
This driver will make CPU Idle calls when Linux is idle (unless this
feature is turned off -- see "Do CPU IDLE calls", below). This
should always save battery power, but more complicated APM features
will be dependent on your BIOS implementation. You may need to turn
this option off if your computer hangs at boot time when using APM
support, or if it beeps continuously instead of suspending. Turn
this off if you have a NEC UltraLite Versa 33/C or a Toshiba
T400CDT. This is off by default since most machines do fine without
this feature.
CONFIG_APM_CPU_IDLE
Enable calls to APM CPU Idle/CPU Busy inside the kernel's idle loop.
On some machines, this can activate improved power savings, such as
a slowed CPU clock rate, when the machine is idle. These idle calls
are made after the idle loop has run for some length of time (e.g.,
333 mS). On some machines, this will cause a hang at boot time or
whenever the CPU becomes idle. (On machines with more than one CPU,
this option does nothing.)
CONFIG_APM_DISPLAY_BLANK
Enable console blanking using the APM. Some laptops can use this to
turn off the LCD backlight when the screen blanker of the Linux
virtual console blanks the screen. Note that this is only used by
the virtual console screen blanker, and won't turn off the backlight
when using the X Window system. This also doesn't have anything to
do with your VESA-compliant power-saving monitor. Further, this
option doesn't work for all laptops -- it might not turn off your
backlight at all, or it might print a lot of errors to the console,
especially if you are using gpm.
CONFIG_APM_RTC_IS_GMT
Say Y here if your RTC (Real Time Clock a.k.a. hardware clock)
stores the time in GMT (Greenwich Mean Time). Say N if your RTC
stores localtime.
It is in fact recommended to store GMT in your RTC, because then you
don't have to worry about daylight savings time changes. The only
reason not to use GMT in your RTC is if you also run a broken OS
that doesn't understand GMT.
CONFIG_APM_ALLOW_INTS
Normally we disable external interrupts while we are making calls to
the APM BIOS as a measure to lessen the effects of a badly behaving
BIOS implementation. The BIOS should reenable interrupts if it
needs to. Unfortunately, some BIOSes do not -- especially those in
many of the newer IBM Thinkpads. If you experience hangs when you
suspend, try setting this to Y. Otherwise, say N.
CONFIG_APM_REAL_MODE_POWER_OFF
Use real mode APM BIOS calls to switch off the computer. This is
a work-around for a number of buggy BIOSes. Switch this option on if
your computer crashes instead of powering off properly.
CONFIG_X86_MCE
Machine Check Exception support allows the processor to notify the
kernel if it detects a problem (e.g. overheating, component failure).
The action the kernel takes depends on the severity of the problem,
ranging from a warning message on the console, to halting the machine.
Your processor must be a Pentium or newer to support this - check the
flags in /proc/cpuinfo for mce. Note that some older Pentium systems
have a design flaw which leads to false MCE events - hence MCE is
disabled on all P5 processors, unless explicitly enabled with "mce"
as a boot argument. Similarly, if MCE is built in and creates a
problem on some new non-standard machine, you can boot with "nomce"
to disable it. MCE support simply ignores non-MCE processors like
the 386 and 486, so nearly everyone can say Y here.
CONFIG_X86_MCE_NONFATAL
Enabling this feature starts a timer that triggers every 5 seconds which
will look at the machine check registers to see if anything happened.
Non-fatal problems automatically get corrected (but still logged).
Disable this if you don't want to see these messages.
Seeing the messages this option prints out may be indicative of dying hardware,
or out-of-spec (ie, overclocked) hardware.
This option only does something on hardware with Intel P6 style MCE.
(Pentium Pro and above, AMD Athlon/Duron)
CONFIG_X86_MCE_P4THERMAL
Enabling this feature will cause a message to be printed when the P4
enters thermal throttling.
CONFIG_TOSHIBA
This adds a driver to safely access the System Management Mode of
the CPU on Toshiba portables with a genuine Toshiba BIOS. It does
not work on models with a Pheonix BIOS. The System Management Mode
is used to set the BIOS and power saving options on Toshiba portables.
For information on utilities to make use of this driver see the
Toshiba Linux utilities web site at:
<http://www.buzzard.org.uk/toshiba/>.
Say Y if you intend to run this kernel on a Toshiba portable.
Say N otherwise.
CONFIG_I8K
This adds a driver to safely access the System Management Mode
of the CPU on the Dell Inspiron 8000. The System Management Mode
is used to read cpu temperature and cooling fan status and to
control the fans on the I8K portables.
This driver has been tested only on the Inspiron 8000 but it may
also work with other Dell laptops. You can force loading on other
models by passing the parameter `force=1' to the module. Use at
your own risk.
For information on utilities to make use of this driver see the
I8K Linux utilities web site at:
<http://www.debian.org/~dz/i8k/>
Say Y if you intend to run this kernel on a Dell Inspiron 8000.
Say N otherwise.
CONFIG_MICROCODE
If you say Y here and also to "/dev file system support" in the
'File systems' section, you will be able to update the microcode on
Intel processors in the IA32 family, e.g. Pentium Pro, Pentium II,
Pentium III, Pentium 4, Xeon etc. You will obviously need the
actual microcode binary data itself which is not shipped with the
Linux kernel.
For latest news and information on obtaining all the required
ingredients for this driver, check:
<http://www.urbanmyth.org/microcode/>.
This driver is also available as a module ( = code which can be
inserted in and removed from the running kernel whenever you want).
The module will be called microcode.o. If you want to compile it as
a module, say M here and read <file:Documentation/modules.txt>. If
you use modprobe or kmod you may also want to add the line
'alias char-major-10-184 microcode' to your /etc/modules.conf file.
CONFIG_X86_MSR
This device gives privileged processes access to the x86
Model-Specific Registers (MSRs). It is a character device with
major 202 and minors 0 to 31 for /dev/cpu/0/msr to /dev/cpu/31/msr.
MSR accesses are directed to a specific CPU on multi-processor
systems.
CONFIG_X86_CPUID
This device gives processes access to the x86 CPUID instruction to
be executed on a specific processor. It is a character device
with major 203 and minors 0 to 31 for /dev/cpu/0/cpuid to
/dev/cpu/31/cpuid.
CONFIG_MAGIC_SYSRQ
If you say Y here, you will have some control over the system even
if the system crashes for example during kernel debugging (e.g., you
will be able to flush the buffer cache to disk, reboot the system
immediately or dump some status information). This is accomplished
by pressing various keys while holding SysRq (Alt+PrintScreen). It
also works on a serial console (on PC hardware at least), if you
send a BREAK and then within 5 seconds a command keypress. The
keys are documented in <file:Documentation/sysrq.txt>. Don't say Y
unless you really know what this hack does.
CONFIG_DEBUG_HIGHMEM
This options enables addition error checking for high memory systems.
Disable for production systems.
CONFIG_DEBUG_KERNEL
Say Y here if you are developing drivers or trying to debug and
identify kernel problems.
CONFIG_DEBUG_SLAB
Say Y here to have the kernel do limited verification on memory
allocation as well as poisoning memory on free to catch use of freed
memory.
CONFIG_DEBUG_IOVIRT
Say Y here to get warned whenever an attempt is made to do I/O on
obviously invalid addresses such as those generated when ioremap()
calls are forgotten. Memory mapped I/O will go through an extra
check to catch access to unmapped ISA addresses, an access method
that can still be used by old drivers that are being ported from
2.0/2.2.
CONFIG_DEBUG_SPINLOCK
Say Y here and build SMP to catch missing spinlock initialization
and certain other kinds of spinlock errors commonly made. This is
best used in conjunction with the NMI watchdog so that spinlock
deadlocks are also debuggable.
CONFIG_DEBUG_BUGVERBOSE
Say Y here to make BUG() panics output the file name and line number
of the BUG call as well as the EIP and oops trace. This aids
debugging but costs about 70-100K of memory.
CONFIG_DEBUG_OBSOLETE
Say Y here if you want to reduce the chances of the tree compiling,
and are prepared to dig into driver internals to fix compile errors.
Software Suspend
CONFIG_SOFTWARE_SUSPEND
Enable the possibilty of suspendig machine. It doesn't need APM.
You may suspend your machine by 'swsusp' or 'shutdown -z <time>'
(patch for sysvinit needed).
It creates an image which is saved in your active swaps. By the next
booting the, pass 'resume=/path/to/your/swap/file' and kernel will
detect the saved image, restore the memory from
it and then it continues to run as before you've suspended.
If you don't want the previous state to continue use the 'noresume'
kernel option. However note that your partitions will be fsck'd and
you must re-mkswap your swap partitions/files.
Right now you may boot without resuming and then later resume but
in meantime you cannot use those swap partitions/files which were
involved in suspending. Also in this case there is a risk that buffers
on disk won't match with saved ones.
SMP is supported ``as-is''. There's a code for it but doesn't work.
There have been problems reported relating SCSI.
This option is about getting stable. However there is still some
absence of features.
For more information take a look at Documentation/swsusp.txt.