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Basic BIOS settings, part 2

Your BIOS has many mysterious screens. In this Daily Drill Down, Ken Dwight probes more mysteries of the BIOS and explores settings that can improve system performance.

You may have wondered about the various settings contained in the BIOS of the machines you support. By changing some of these settings, you can improve the performance of the computer, resolve hardware conflicts, and prevent some problems from arising in the first place. This Daily Drill Down continues the documentation of basic BIOS options that are most likely to be useful to you in troubleshooting system problems and enhancing overall performance.

Setup options
In part 1, I described the functions of the BIOS chip, provided information on the BIOS manufacturers, and discussed three BIOS screens:
  • Standard CMOS Setup
  • BIOS Features Setup
  • Chipset Features Setup
  • Load Setup Defaults

In this Daily Drill Down, I cover the following screens:
  • Power Management Setup
  • Integrated Peripherals
  • PNP/PCI Configuration
  • Password Settings (User, Supervisor, Power On)

Just a note of warning—even different versions of a BIOS from the same manufacturer may have different options, and in some cases they may appear on different screens. If you don’t see a particular feature or option on the screen described here, look around on other screens and see if the BIOS provider has chosen a different place to put it.

Power Management Setup
This screen is used to define the power-management features you want to enable on this computer and the various types of power savings they can effect. There are two types of power management that may be available on your computer: APM and ACPI.

APM, or Advanced Power Management, is the original form of the power-conservation measures that were introduced to reduce power consumption and conceivably extend the life of various system components. If your BIOS supports APM, you will have a screen in the Setup menu that lets you specify the degree of power-management functionality you want to use.

A newer form of power management supported by the latest BIOSs and operating systems is ACPI, which stands for Advanced Configuration and Power Interface. ACPI is available only under Windows 98, Millennium Edition, and Windows 2000. (For more information on ACPI, see “Are you sleeping? Understanding hibernation, standby, and other power management features.”)

One major benefit of ACPI is the fact that all power-management settings are done in the OS rather than the BIOS. This single point of control eliminates many of the conflicts that are based on incompatibilities between APM BIOS settings and Windows Control Panel settings; some vendors also had their own proprietary power-management software that further muddied the waters.

If you’re using APM, you may specify which levels of power management to employ and the time intervals that trigger them. Most BIOSs offer Minimum Saving, Maximum Saving, User Defined, and None settings. There are times you will want to be sure that power management is set to None.

For instance, if a system is sharing files across a network, either as a file server or on a peer-to-peer network, you probably don’t want any power-management functionality. If a system is in Suspend mode or has been powered down by APM, its shared files won’t be available to other users on the network.

Another time you may not want to use power management is when you’re having trouble coordinating the power-management settings in the BIOS, other hardware components, the operating system, and vendor-provided software. Sometimes it’s just more trouble than it’s worth.

When you use APM, the Min Saving and Max Saving options define default times after which various power-conservation measures are invoked. These measures may include blanking or turning off the monitor, powering down the hard drive, reducing the processor speed, and possibly other steps in APM-compliant devices.

If you choose User Defined, you are given the option to specify the steps that are to be taken and the times that define inactivity before that step is to be performed. Regardless of the degree of power management you choose, you can also define various events that will wake up a system that has been put into Standby or Suspend mode by APM.

The Power Management Setup screen allows you to specify the devices or IRQs that will cause the system to return to the Full On state from Standby or Suspend mode. For example, if this system is being used as a fax server, it may go into one of these power-saving modes in the middle of the night if no faxes have been received. By enabling the appropriate serial port, you can allow the system to wake up when an IRQ is raised as a result of an incoming ring signal on the modem.

Integrated Peripherals
This screen gives you the ability to enable or disable various subsystems that are integral to the motherboard, such as primary and secondary IDE controllers, floppy disk controllers, and serial and parallel ports. In some cases, you can also change the hardware resources that are assigned to the devices or the mode in which the device is to function.

There are several reasons that you may want to change some of these settings. One example would be the situation where a motherboard component is not being used and you want to make those resources available to other devices. For instance, if your motherboard has integrated USB ports but you aren’t using any USB devices, then you may want to disable that function in order to free up the IRQ allocated to the USB ports.

Note that if you are successfully using a serial or USB mouse, you won’t need the PS/2 mouse port that is standard on most motherboards. In order to free up IRQ 12 for other possible use, you’ll need to disable the PS/2 mouse port. On some BIOSs, this setting is not found on this screen; instead, you may find a setting on the BIOS Features Setup screen entitled PS/2 Mouse Function Control or similar wording.

Another common reason for changing settings in this screen would be a scenario where you have purchased and want to install a new Ultra ATA/66 hard drive. On all but the newest motherboards, the integrated IDE controllers are unable to realize the full potential of such a drive. To take advantage of the maximum transfer rate supported by the drive, you’ll need to install an Ultra ATA/66 IDE controller.

Usually when you install such an improved IDE controller, you’ll want to disable the onboard IDE controllers, or possibly just the primary IDE controller, or perhaps both primary and secondary. The final decision would be based on the total capabilities of the new Ultra ATA/66 controller and the total number of IDE devices you need to attach to this system.

A third reason for changing settings in this screen is when you install an internal modem. You may want the modem to use COM1 and its associated IRQ and I/O address, but the onboard COM ports normally have appropriated those resources. By using the Onboard Serial Port 1 and Onboard Serial Port 2 settings, you can disable one of the onboard COM ports or reassign its resources to make the COM1 settings available for your modem.

One other time you may need this screen is in the rare event that one or more of the on-board device controllers fail. In that case, you can add an expansion card to take over that function, which usually will require that you disable the on-board device to prevent resource conflicts.

PNP/PCI Configuration
This screen is used to define the Plug and Play capabilities supported by this motherboard, BIOS, and operating system. You may be surprised by some of the settings that presently are in effect on your computer.

PNP OS Installed
This entry designates whether your system is running a Plug and Play (PnP) operating system, such as Windows 95/98 or Windows 2000. If it is, then this option probably should be set to Yes. It may surprise you to find that your BIOS might be set to No, even though you are in fact running a Plug and Play operating system.

The reality is that PnP operating systems provide PnP functionality even with this option set to No. All capabilities of PnP will not be available, however, so you usually will want to be sure this is set to Yes if the system is running a PnP OS.

The possible exception is if you have old, 16-bit ISA expansion cards in the system, which may not be fully PnP-compliant, if at all. In order to make those boards work properly, you may need to configure them manually instead of depending on PnP.

Resources Controlled By
This screen is where you specify how the various expansion cards in the system are configured. If all of your add-in cards are PCI- or PnP-compliant ISA boards, you’ll want to choose Automatic for this option. That selection gives PnP the ability to assign any available IRQ and DMA channel to any devices that require them.

If you have non-PnP boards in the system, you’ll need to set this option to Manual and then specify the resource requirements for these devices. For each IRQ, complete the “assigned to” portion. The settings appear in the BIOS as shown in this table:

IRQ-n assigned to
DMA-n assigned to

These settings let you specify the type of device that will be using each of the designated IRQs and DMA channels. For each entry, you will choose either PCI/ISA PnP or Legacy ISA Device. The only entries you will need to make here are the hardware resources used by any non-PnP, or legacy, devices.

The default setting for each resource is PCI/ISA PnP, so you won’t need to change many of these lines. You may occasionally encounter a device that claims to be PnP-compliant but doesn’t function properly when PnP assigns its resources. In such a case, one possible way of making it perform correctly is to manually force these settings for the device by defining the required IRQ and/or DMA channel as belonging to a legacy device.

The Assign IRQ For VGA and Assign IRQ For USB settings let you free up IRQs that may be assigned by default but are not really required in this system. If you have only one video display adapter, are running only 2D graphics, and have no TV tuner or other exotic video devices attached, you don’t need an IRQ for VGA. So here’s your opportunity to give yourself another IRQ for use by PnP or for manual assignment. Just change this setting to Disabled.

By the same token, if your motherboard has USB ports installed, by default an IRQ will be reserved for USB communications. If you don’t have any USB devices attached to the system, then you don’t need this IRQ either. Set Assign IRQ For USB to Disabled, and you’ve picked up another available IRQ.

Supervisor Password, User Password
These screens allow you to set or change a password that is required in order to change BIOS settings or to power up the machine at all. This functionality gives you a measure of security to prevent unauthorized users from accessing the computer or making potentially dangerous changes to the CMOS.

Some BIOSs have a single menu selection that simply references passwords; that screen may allow you to set or change the different types of passwords individually. Your BIOS may let you specify the type of password in the BIOS Features screen. If you see a security option, it may let you specify a setup, user, or other type of password.

The potential problem with this option is that you may forget the password and be unable to accomplish the work you need to do on the computer—you may not even be able to turn it on! If this ever happens to you, the motherboard probably has a provision for clearing the passwords or even clearing all of CMOS memory. (Passwords, like all the other BIOS settings, are stored in the system’s CMOS.)

The most reliable information on clearing passwords will be found in the motherboard’s documentation. You may have a jumper with two possible settings, Normal or Clear; you may see a jumper labeled CPW (Clear Password) or RPW (Reset Password). Some motherboards have a notation adjacent to two solder points, “Short Here To Clear CMOS.” And some motherboards have this option but don’t document it on the board itself as a security measure. That’s when you really must have the documentation.

In any event, there’s no way to “crack” any of these BIOS passwords. The best you can hope for is to clear them and set them to a known value or to None. Worst case, if you can’t find any provisions for clearing the passwords, you could always remove the CMOS battery and wait for the BIOS to forget everything and then go back to the procedures you’d follow after normal battery expiration/replacement.

This Daily Drill Down concludes my discussion of BIOS settings. I’ve gone over most of the BIOS settings you’re likely to need to understand and modify. Any time your motherboard documentation conflicts with statements made here, trust the documentation first. The settings I described are generally useful, but there are so many possible variations in features, locations, and potential values that it’s safe to say, “Your mileage may vary.” Good luck!
The authors and editors have taken care in preparation of the content contained herein but make no expressed or implied warranty of any kind and assume no responsibility for errors or omissions. No liability is assumed for any damages. Always have a verified backup before making any changes.

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