Appendix B. BIOS Settings

The BIOS, or Basic Input-Output System, is the program (stored in a chip on your motherboard) responsible for booting your computer and starting your operating system. It also handles the flow of data between the operating system and your peripherals (keyboard, mouse, hard disk controller, video adapter, etc.). Your BIOS has a special "setup" screen that allows you to customize its settings to enable or disable motherboard features, improve performance, and sometimes, fix problems.

The BIOS setup is usually accessed by pressing a key such as Del, F2, or Esc immediately after powering on your system and before the initial beep. The screen that appears before the Windows logo typically identifies the key used to enter setup; consult your computer's manual if you need further help.

The settings available in a computer's BIOS setup screen will vary significantly from one system to another, but there are some settings that are common throughout them all. The problem is that motherboard and computer manufacturers are notorious for poorly documenting BIOS settings, so it can be difficult to determine what the settings mean, let alone how they should be set.

Here are some tips for working with BIOS settings and the descriptions in this appendix:

  • If you're trying to fix a problem, don't change more than one BIOS setting at a time. Although it may take longer, it means you can determine which setting is responsible for fixing the problem (or causing a new one).

  • The BIOS is typically stored on a "flash" chip, which means it can be updated with newer versions. Check with your motherboard manufacturer to see if a newer BIOS is available for your system. In most cases, BIOS updates only fix bugs, but they occasionally can improve performance or add support for new hardware. If you're unable to install Windows XP (or its successor) on your system, an outdated BIOS may be to blame.

     

    Flashing a BIOS is a risky procedure. If something goes wrong (i.e., the power goes out, or the BIOS turns out to be corrupted or the wrong version), your computer will probably not boot. Most motherboard manufacturers provide a BIOS recovery method, typically involving a floppy diskette and a special keystroke combination, but if the computer won't boot, you won't be able to look it up on the Web after the fact. For this reason, you'll want to make sure you've familiarized yourself with the procedure before you attempt to update your BIOS.

     

  • Keep in mind that the names of BIOS settings listed here may vary, and one appendix can't possibly accommodate them all. For example, a setting named Event Log on one system might be called System Event Log on another. If you can't find a particular setting, try looking through the list for variations.

  • One of the problems with the BIOS setup screen is that you can't access it from within Windows, which means you can't look up settings on the Web, you can't take screenshots, and you can't take notes without using a pen and paper. However, a digital camera can be very handy for all of these; just take one or photos of your screen (with the flash turned off, of course) to quickly record all your BIOS settings.

Table B-1 lists many common BIOS settings, along with brief explanations and some tips. For more extensive BIOS setting information and advice, check out the "The Definitive BIOS Optimization Guide" at http://www.rojakpot.com.

 

Table B-1. Common BIOS settings and what they mean

Setting

Description

AC Power Recovery

Determines whether or not the computer turns on automatically when power is applied (such as from a power loss or external power switch.

ACPI Aware O/S

See "Power Management."

AddOn ROM Display Mode

Choose whether the startup screen is handled by the primary BIOS or a secondary "add-on" BIOS. In most cases, you'll want to disable this option.

Address Range Shadowing

Various hardware address ranges can be "shadowed," which means that pieces of faster system RAM are substituted for them. In most cases, this is not a good idea, so it is recommended that shadowing be disabled for all address ranges.

AGP 2X/4X Mode

The AGP 2X and 4X modes double and quadruple the bandwidth to your AGP video card, respectively, but can only be used if your video card supports 2X or 4X.

AGP Aperture/Device Address Space Size

This sets the amount of system memory used to store textures for 3D graphics. The more video memory you have, the lower this setting should be. Many video problems are caused by this value being set too high. Try a value of 32MB.

Anti-Virus Protection

Actively scans your hard disk for boot sector viruses. Despite the apparent usefulness of a feature like this, you should always disable it, as it typically interferes with Windows and causes all sorts of problems.

APM Enable

See "Power Management."

Assign IRQ For USB

See "Legacy USB Support."

Assign IRQ For VGA

This should be enabled only if your video card does not need its own IRQ and you need an extra IRQ for another device.

Auto Power On

See "AC Power Recovery."

Boot Device Priority/Boot Sequence

Specifies the order among the various drives in your system that your computer looks for a drive with a bootable operating system. For example, if your CD drive has a higher boot priority than your hard drive, then your computer will look for a bootable CD in your CD drive before it attempts to boot off the hard disk. If the CD drive has a lower boot priority, and Windows is installed on your hard disk, your computer will ignore bootable CDs.

Boot Other Device

If an operating system isn't found on the first boot drive (see "Boot Device Priority/Boot Sequence") and this setting is enabled, your computer will attempt to boot off of other drives.

Boot Sector Virus Protection

See "Anti-Virus Protection."

Boot to OS/2

Changes how memory above 64MB is handled for compatibility with IBM's defunct OS/2 operating system. For obvious reasons, this option should be disabled.

Bootup CPU Speed

This is a remnant of the "turbo" button found on old 486 computers, allowing you to slow down the machine for old games. There's little reason you'd want any other setting than "Fast" here.

Bootup Numlock Status

See "Numlock State."

C000/C400/C800/CC00 16k Shadow

See "Address Range Shadowing."

Chassis Fan

This shows the RPM of the fan connected to the "Chassis Fan" connector on your motherboard. This is typically a read-only setting.

CPU Current Temperature

This shows the measured temperature of your processor. For dual-processor systems, you'll see two such settings. This is typically a read-only setting.

CPU Fan

This shows the RPM of the fan connected to the "CPU Fan" connector on your motherboard. For dual-processor systems, you'll see two such settings. This is typically a read-only setting.

CPU Level 1 Cache/Level 2 Cache

These settings allow you to disable your processor's primary (level 1) and secondary (level 2) cache, respectively. These settings should always be enabled.

CPU to PCI Write Buffer

Enables or disables the buffer used for data sent to the PCI bus by the processor. This should be enabled.

D000/D400/D800/DC00 16k Shadow

See "Address Range Shadowing."

Delayed Transaction

See "PCI 2.1 Compliance."

Diskette

See "Floppy"

DRAM Data Integrity Mode

If you're using ECC (Error Checking and Correction) memory, set this to ECC. Otherwise, choose Non-ECC.

EMM386 Support

Enable this only if you're booting to DOS and need to support the now-defunct EMM386.SYS driver.

Event Log

Your motherboard can log errors (such as BIOS problems and hard disk boot problems) it encounters during startup. Settings in this section allow you to enable or disable logging, view the log, erase the log, etc.

Fast Boot

See "Quick Boot."

First Boot Device

See "Boot Device Priority/Boot Sequence."

Flash BIOS Protection

This prevents the bios from being overwritten or updated. You'll need to disable this to update your BIOS, as explained at the beginning of this appendix. Otherwise, leave this enabled to protect against viruses that attack BIOSes.

Floppy Drive A/B

Use these settings to define the floppy diskette drives you have connected to your computer.

Floppy Drive Seek

When enabled, this option will send a signal to your floppy drive(s) to help detect certain drive characteristics. Leave this off for a quicker boot.

Floppy Write Protect

This prevents anyone from writing data to a diskette in your floppy drive, useful if the computer is in a public place and you don't want people copying data to floppies.

GART W2K Miniport Driver

The GART (Graphics Address Remapping Table) is part of the AGP subsystem. In most cases, you want to disable this option.

Green PC Monitor Power State

If you're using an APM (advanced power management)-compliant "green pc" monitor, this setting allows you to automatically shut it off after a certain perioud of inactivity, in lieu of a screen saver. With these types of settings, it's best to let Windows XP control how and when devices are shut off.

Hard Disk Power Down Mode

Windows can shut down your hard disk to save power after a certain period of inactivity. With these types of settings, it's best to let Windows XP control how and when devices are shut off.

Hard Disk Write Protect

This option write-protects your hard disk so data can't be written to it. You won't want to use this on a Windows XP machine.

Hard-Disk Drive Sequence

If you have more than one hard disk drive on your IDE controller, this option allows you to choose the order in which your computer looks for bootable drives. Used in conjunction with "Boot Device Priority/Boot Sequence."

Hardware Reset Protect

Prevent the computer from being restarted with the Reset button on the front of your computer's case. Helpful if you have a dog who likes to wag his/her tail while standing next to your computer.

HDD S.M.A.R.T. Capability

Enables the S.M.A.R.T. (Self Monitoring Analysis And Reporting) feature supported by most modern hard disks, that helps predict potential problems before they happen. Most users don't need it, and are probably better off disabling this feature.

Hit DEL Message Display

Turns on or off the message on the POST (Power On Self Test) screen that says "Press DEL to enter Setup."

IDE BusMaster

See "PCI IDE BusMaster."

IDE Controller

Enable or disable either or both of the IDE controllers on the motherboard. Each controller supports up to two devices (a "master" and a "slave"), but if you only have two devices, you can hook them both up to your primary IDE controller and disable the secondary controller. Disabling the controllers you don't need frees IRQs for other devices in your system, but distributing your devices across your controllers can improve performance.

IDE HDD Block Mode

Although enabling this option should improve performance on some systems, it should not be used with Windows XP.

Internal Cache

See "CPU Level 1 Cache."

IRQ3, IRQ4, IRQ5, etc.

There are two different settings named for IRQs. One, used with power management, determines whether or not your computer monitors a given IRQ for activity (used to "wake up" the system). The other, typically found in the PCI section, allows to you "reserve" an IRQ and prevent the Plug-and-Play system from automatically assigning it to a device.

Legacy USB Support

Enable this option if you're using a USB keyboard or USB mouse and you want to use them in the BIOS setup screen, DOS, or some other environment outside of Windows.

Master/Slave Drive UltraDMA

This should be enabled for drives that support UltraDMA, and disabled otherwise. In most cases, it should be set to Auto.

Memory Hole at 15M-16M

Enable this option to reserve this segment of your computer's memory for use by some older ISA cards. Unless you specifically need it, this option should be disabled.

Memory Write Posting

This option may improve performance on older systems, but will likely degrade performance and even cause video corruption on newer systems. Disable this option unless you're willing to experiment with it.

MPS Version Control

This allows you to choose the multi-processor specification version supported by your operating system. Windows XP supports version 1.4, although some other operating systems do not.

Numlock State

Turn this on if you want the Num Lock keyboard light turned on when the system starts. Turn this off if you typically use the numeric keypad to move your cursor, instead of the "inverted T" cursor keys.

Onboard FDD Controller

This enables or disables the floppy diskette drive controller on your motherboard.

Onboard IR Function

This enables or disables the infrared port on your motherboard.

Onboard SCSI

This enables or disables the SCSI controller on your motherboard. Note that SCSI settings will typically be set with a separate SCSI BIOS utility. For instance, most Adaptec controllers are configured by pressing Ctrl-A at the screen that lists SCSI devices during bootup.

Overheat Warning Temperature

This sets the temperature above which the overheat warning is triggered. See "System Overheat Warning," later in this appendix, for more information.

Parallel Port

This enables or disables the parallel (printer) port on your motherboard

Parallel Port Mode

Use this to choose between the various parallel (printer) port modes: ECP, EPP, ECP+EPP, Normal (SPP). In most cases, you'll want ECP; only choose one of the lesser options if you run into a compatibility problem. Note that such problems are more commonly caused by incorrect or faulty printer cables.

PCI 2.1 Compliance

This should be enabled, unless you have one or more PCI cards that are not compatible with the PCI 2.1 specification.

PCI IDE BusMaster

Enables or disables bus mastering for the IDE controller, which helps reduce load on the processor when data is transferred to and from IDE devices. Disable if you're using older drives that don't support bus mastering.

PCI IRQ Assignment

This setting (usually a group of settings) allows you to assign IRQs to specific PCI slots.

PCI Latency Timer

This sets the number of cycles during which a single PCI device can monopolize the PCI bus. Increase this value for better performance, or decrease it if you run into problems. The default is typically 32 cycles, but you may have success with 64 or 128 cycles.

PCI Pipelining

Enable this to improve performance with your video adapter.

PME Resume

See "Remote Wake Up."

PnP OS Installed

This allows your operating system's Plug-and-Play feature to control the resources used by the various devices in your system. Enable this option for Windows XP, or disable it if you're using an OS that doesn't support PnP.

Power Button Mode

This allows you to choose whether your computer's power button shuts off the computer (after holding it for four seconds) or forces your computer to enter a "hibernate" state.

Power Lost Control

Determines what happens when power is lost and then reapplied to the system. Choose Always On if you want the system to power up automatically(useful for servers), or Always Off to leave it off until the power button is pressed. Note that some systems will power themselves on after a power outage, even if they were powered down beforehand.

Power Management

This allows your operating system's APM (Advanced Power Management) feature to turn off the various devices in your system to save power. Enable this option for Windows XP, or disable it if you're using an OS that doesn't support APM.

Power On Function

Use this option to enable other ways to turn on your computer, such as the "power on" button on your keyboard (if applicable).

Primary Display

Allows you to choose whether your PCI or AGP adapter is used as your primary display when using multiple video cards.

Primary IDE Master

Specify the type of drive connected to your primary IDE controller, and set as the "master" (typically with a jumper).

Primary IDE Slave

Specify the type of drive connected to your primary IDE controller, and set as the "slave" (typically with a jumper).

Processor Serial Number

Enable this only if you want your operating system to be able to read the serial number of your processor. Since this can cause substantial security and privacy problems, this option should be disabled unless you specifically need it.

Processor Speed

This is typically a read-only setting that shows the speed of your processor (in Mhz or Ghz). Some motherboards allow you to "overclock" your processor, forcing it to run faster than its rated speed.

Processor Type

This read-only setting tells you what type of processor is currently installed.

PS/2 Mouse Support

Use this to enable or disable your PS/2 mouse port. Disable this if you're using a USB or serial-port mouse, and wish to free up IRQ 12 for another device.

PXE Resume

See "Remote Wake Up."

Quick Boot

Turn this on to skip the thorough, slow memory test performed when the computer is first turned on, allowing a faster boot. It's a good idea to disable this option and sit through the test when first installing new RAM, but once the memory has been tested, it's fine to skip it.

Quiet Boot

A "quiet" boot is one where your motherboard manufacturer's logo is displayed on the screen instead of the details, such as the amount of memory, detected disks, and BIOS revision date. Disable this option (or press ESC while looking at the logo) to show this information.

Read-Around-Write

When this setting is enabled, your processor can read directly from the cache, without waiting for it to be written to memory first. Enable this feature for better performance.

Remote Wake Up

This feature allows your computer to be turned on a signal from another computer on your network. Disable this feature unless you specifically need this functionality. See http://www.annoyances.org/exec/show/article04-101 for details.

Report no FDD for Win95

If this setting is disabled, your BIOS will not identify a missing floppy diskette drive to a Windows 9x/Me system. Enable this option for Windows XP.

Reset Config Data

If enabled, the PnP (Plug-&-Play) subsystem will reset and reconfigure all of your PnP devices every time your system starts. Use this only if one or more devices needs to be reset to function.

SDRAM CAS Latency

In theory, set this to CAS2 if your memory is rated at CAS Latency 2; otherwise, use CAS3. Interestingly, you should be able to use the faster CAS2 setting regardless of the type of installed memory; use CAS3 only if instability results.

Second Boot Device

See "Boot Device Priority/Boot Sequence."

Secondary IDE Master

Specify the type of drive connected to your secondary IDE controller, and set as the "master" (typically with a jumper).

Secondary IDE Slave

Specify the type of drive connected to your secondary IDE controller, and set as the "slave" (typically with a jumper).

Serial Port 1/2Serial Port A/B

The numbers (or letters) have no correlation to the well-known COM1/COM2 designations, but rather to each of the two physical ports on your motherboard. Set the ports as follows: "3F8/IRQ4" to assign the port to COM1, "2F8/IRQ3" for COM2, "3E8/IRQ4" for COM3, or "2E8/IRQ3 to make it COM4. Disable any port you're not using so it won't consume any resources you can use for other devices. Make sure the two ports don't conflict with each other, or any other devices in your system (such as your modem).

Supervisor Password

This setting allows you to password-protect your BIOS setup. Note that if you forget the password (or simply wish to bypass such a restriction), just reset the BIOS configuration; this is typically done with a jumper, but can also be accomplished by disconnecting the motherboard battery for about twenty minutes.

Suspend Mode

Choose whether the computer is placed in "suspend" or "hibernate" power-saving modes.

Suspend Timeout

Specifies the number of minutes of inactivity before the system is placed in "suspend" power-saving mode.

System BIOS Cacheable

This is similar to "Address Range Shadowing," except that it works with your motherboard's BIOS. Disable this option for best performance.

System Date/Time

Sets your computer's internal clock. This can also be changed by going to Control Panel figs/u2192.gif Date and Time.

System Keyboard

Disable this option if there's no keyboard attached.

System Memory

In most computers, this will be a read-only setting that displays the amount of installed RAM. However, as a holdover from older computers, you may have to enter the BIOS setup screen and then exit for the computer to recognize newly-installed memory, even though you won't be able to directly modify this setting.

System Overheat Warning

Enable this to sound an alarm or flash a light if your computer's internal temperature exceeds the value set with the "Overheat Warning Temperature"

Third Boot Device

See "Boot Device Priority/Boot Sequence."

Typematic Rate/Delay

Faster settings will make your keyboard more responsive outside of Windows, but within Windows, these settings are overridden by those found in Control Panel figs/u2192.gif Keyboard.

USB Function

See "Legacy USB Support"

VGA Palette Snoop

Enable this only if you're using an add-on card that connects to the "Feature Connector" found on older video cards, and then only if the device specifically requires this setting.

Video BIOS Shadow/Video BIOS Cacheable

This is similar to "Address Range Shadowing," except that it works with the BIOS of your video adapter. This is a holdover from early video cards, and should be disabled in any modern system.

Video Power Down

If enabled, your computer will be able to shut down your video card and monitor to save power. Typically, it's best to have Windows control power-saving features by going to Control Panel figs/u2192.gif Power Options.

Video RAM Cacheable

This is similar to "Address Range Shadowing," except that it works with the memory installed on your video card. This option should always be disabled.

Virus Warning

See "Anti-Virus Protection."

Wait for F1 if Error

If this option is disabled, your computer will continue to boot, even if an error is found; otherwise, you'll have to press F1 before the system will boot. Such errors include a missing keyboard, a missing video adapter, and an unexpected quantity of installed memory.

Write combining

Enable this option for better video performance, but disable it if you encounter video corruption or system crashes. A related setting can be found in Control Panel figs/u2192.gif Display figs/u2192.gif Settings tab figs/u2192.gif Advanced figs/u2192.gif Troubleshoot tab.

 



Windows XP Annoyances
Fixing Windows XP Annoyances
ISBN: 0596100531
EAN: 2147483647
Year: 2005
Pages: 78
Authors: David A. Karp

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