Home > Articles > Hardware > Upgrading & Repairing

This chapter is from the book

Plug-and-Play BIOS

The role of the traditional BIOS was to manage the essential devices in the system: the hard drive, floppy drive, video, parallel and serial ports, and keyboard and system timer. Other devices were left to fight for the remaining IRQs and other hardware resources listed in Chapter 2, "System Components and Configuration." When Windows 95 was introduced, the role of the BIOS changed dramatically. To support Windows 95, the Plug-and-Play BIOS was introduced, changing how cards were installed and managed. Table 3.2 compares a Plug-and-Play (PnP) BIOS to a conventional BIOS.

Table 3.2 Plug-and-Play BIOS Versus Conventional BIOS


Conventional BIOS

Plug-and Play BIOS

Hardware configuration devices and video only


All PnP devices as well as motherboard devices

Configuration type

Static (fixed settings)

Dynamic (settings can be altered as various devices are installed)


Manual configuration

Manual, BIOS-assisted, or operating method system assisted

Operating system relationship to BIOS

Accepts all BIOS settings without alteration

Receives PnP device information from BIOS and can alter settings as required


A complete list of PnP device IDs is found in the Technical Reference section of the CD included with Upgrading and Repairing PCs, 13th Edition.

PnP BIOS Configuration Options

Although PnP BIOSes vary widely in their features, the following settings are typical. Use the list in Table 3.3, along with the tables that follow, to help you make configuration changes when necessary.

Resource Configuration

The Resource Configuration menu is used for configuring the memory and interrupt usage of non–Plug-and-Play (legacy) ISA bus-based devices. Table 3.3 shows the functions and options found in a typical modern BIOS.

Table 3.3 Typical Resource Configuration Menu1




Memory Reservation

C800 CBFF Available (default) | Reserved

CC00 CFFF Available (default) | Reserved

D000 D3FF Available (default) | Reserved

D400 D7FF Available (default) | Reserved

D800 DBFF Available (default) | Reserved

DC00 DFFF Available (default) | Reserved

Reserves specific upper memory blocks for use by legacy ISA devices.



IRQ 3 Available (default) | Reserved

IRQ 4 Available (default) | Reserved

IRQ 5 Available (default) | Reserved

IRQ 7 Available (default) | Reserved

IRQ 10 Available (default) | Reserved

IRQ 11 Available (default) | Reserved

Reserves specific IRQs for use by legacy ISA devices. An asterisk (*)displayed next to an IRQ indicates an IRQ conflict.

Note that these settings are only for legacy (non–Plug-and-Play) ISA devices. For all Plug-and-Play ISA devices as well as PCI devices (which are Plug-and-Play by default), these resources are instead configured by the operating system or by software that comes with the cards.

Setting these resources here does not actually control the legacy ISA device; that usually must be done by moving jumpers on the card. By setting the resource as reserved here, you are telling the Plug-and-Play operating system that the reserved resources are off-limits, so it won't accidentally set a Plug-and-Play device to use the same resource as a legacy ISA device. Reserving resources in this manner is sometimes required because the Plug-and-Play software can't detect all legacy ISA devices and therefore won't know which settings the device might be using.

In a system with no legacy devices, reserving any resources via this menu is not necessary. To enable more options for the increasing number of PCI/PnP slots and cards found on recent systems, you can disable reservation for legacy devices that you don't use. For example, if you don't use LPT 1 (IRQ 7) and COM 2 (IRQ 3) ports, disable them in the BIOS and set these IRQs as available for PCI/PnP devices.

Some boards have additional configuration options for the Plug-and-Play (PnP) BIOS features as well as the PCI bus. These features are largely chipset-dependent, but some common examples are shown in Table 3.4.

Table 3.4 Typical PnP and PCI Options1

DMA Assigned to

When resources are controlled manually, assign each system DMA channel as one of the following types, depending on the type of device using the interrupt:

Legacy ISA devices compliant with the original PC AT bus specification, requiring a specific DMA channel.

PCI/ISA PnP devices compliant with the Plug-and-Play standard, whether designed for PCI or ISA bus architecture.

PCI IRQ Activated by

Leave the IRQ trigger set at Level unless the PCI device assigned to the interrupt specifies edge-triggered interrupts.


This field enables you to select PCI IDE IRQ mapping or PC AT (ISA) interrupts. If your system does not have one or two PCI IDE connectors on the system board, select values according to the type of IDE interface(s) installed in your system (PCI or ISA). Standard ISA interrupts for IDE channels are IRQ 14 for primary and IRQ 15 for secondary.

Primary/Secondary IDE INT#

Each PCI peripheral connection is capable of activating up to four interrupts: INT# A, INT# B, INT# C, and INT# D. By default, a PCI connection is assigned INT# A. Assigning INT# B has no meaning unless the peripheral device requires two interrupt services rather than one. Because the PCI IDE interface in the chipset has two channels, it requires two interrupt services. The primary and secondary IDE INT# fields default to values appropriate for two PCI IDE channels, with the primary PCI IDE channel having a lower interrupt than the secondary.

Note that all single-function PCI cards normally use INT# A, and each of these must be assigned to a different and unique ISA interrupt request (IRQ).

Used Mem Base Addr

Select a base address for the memory area used by any peripheral that requires high memory.

Used Mem Length

Select a length for the memory area specified in the previous field. This field does not appear if no base address is specified.

Assign IRQ for USB

Select Enabled if your system has a USB controller and you have one or more USB devices connected. If you are not using your system's USB controller, select Disabled to free the IRQ resource.

When to Use the PnP BIOS Configuration Options

In an ideal situation involving PnP-aware operating systems such as Windows 9x/Me or 2000/XP, a computer with a PnP BIOS, and a PnP device, the BIOS detects the PnP device and Windows configures it without user intervention. Table 3.5 lists the circumstances under which you might need to use PnP BIOS configuration options.

Table 3.5 Solving Configuration Problems with the PnP BIOS Configuration Options




Legacy (non-PnP) card needs particular IRQ or DMA setting already in use by PnP device.

Set DMA and IRQ used by legacy card to ISA option in BIOS.

This prevents PnP devices from using the resource; verify that legacy card setting matches BIOS selections.

Windows 9x/Me/2000/XP is not detecting and configuring PnP devices not needed at boot time (such as modems, printers, and so on).

Set Plug and Play Aware Operating System option to Yes in BIOS.


PCI video card is assigned an IRQ that you need for another device.

Set Assign IRQ to VGA option to No in BIOS.

This frees up the IRQ with out ill effects in some cases; might not work if the card is used for MPEG movie playback. Do not use for AGP video cards.

New PnP device can't be detected by the system.

Set PCI Slot x IRQ Priority to desired (unused) IRQ; install card into designated PCI slot.

If setting the IRQ for the PCI slot doesn't work, remove all non-essential PnP cards, install new PnP card first, and then reinstall others.

New PnP device interferes

Check system manual to determine whether the slot that is used shares an IRQ with another slot or with an onboard device.

Using a different slot for the with existing PnP device new PnP device can avoid conflicts.

InformIT Promotional Mailings & Special Offers

I would like to receive exclusive offers and hear about products from InformIT and its family of brands. I can unsubscribe at any time.


Pearson Education, Inc., 221 River Street, Hoboken, New Jersey 07030, (Pearson) presents this site to provide information about products and services that can be purchased through this site.

This privacy notice provides an overview of our commitment to privacy and describes how we collect, protect, use and share personal information collected through this site. Please note that other Pearson websites and online products and services have their own separate privacy policies.

Collection and Use of Information

To conduct business and deliver products and services, Pearson collects and uses personal information in several ways in connection with this site, including:

Questions and Inquiries

For inquiries and questions, we collect the inquiry or question, together with name, contact details (email address, phone number and mailing address) and any other additional information voluntarily submitted to us through a Contact Us form or an email. We use this information to address the inquiry and respond to the question.

Online Store

For orders and purchases placed through our online store on this site, we collect order details, name, institution name and address (if applicable), email address, phone number, shipping and billing addresses, credit/debit card information, shipping options and any instructions. We use this information to complete transactions, fulfill orders, communicate with individuals placing orders or visiting the online store, and for related purposes.


Pearson may offer opportunities to provide feedback or participate in surveys, including surveys evaluating Pearson products, services or sites. Participation is voluntary. Pearson collects information requested in the survey questions and uses the information to evaluate, support, maintain and improve products, services or sites, develop new products and services, conduct educational research and for other purposes specified in the survey.

Contests and Drawings

Occasionally, we may sponsor a contest or drawing. Participation is optional. Pearson collects name, contact information and other information specified on the entry form for the contest or drawing to conduct the contest or drawing. Pearson may collect additional personal information from the winners of a contest or drawing in order to award the prize and for tax reporting purposes, as required by law.


If you have elected to receive email newsletters or promotional mailings and special offers but want to unsubscribe, simply email information@informit.com.

Service Announcements

On rare occasions it is necessary to send out a strictly service related announcement. For instance, if our service is temporarily suspended for maintenance we might send users an email. Generally, users may not opt-out of these communications, though they can deactivate their account information. However, these communications are not promotional in nature.

Customer Service

We communicate with users on a regular basis to provide requested services and in regard to issues relating to their account we reply via email or phone in accordance with the users' wishes when a user submits their information through our Contact Us form.

Other Collection and Use of Information

Application and System Logs

Pearson automatically collects log data to help ensure the delivery, availability and security of this site. Log data may include technical information about how a user or visitor connected to this site, such as browser type, type of computer/device, operating system, internet service provider and IP address. We use this information for support purposes and to monitor the health of the site, identify problems, improve service, detect unauthorized access and fraudulent activity, prevent and respond to security incidents and appropriately scale computing resources.

Web Analytics

Pearson may use third party web trend analytical services, including Google Analytics, to collect visitor information, such as IP addresses, browser types, referring pages, pages visited and time spent on a particular site. While these analytical services collect and report information on an anonymous basis, they may use cookies to gather web trend information. The information gathered may enable Pearson (but not the third party web trend services) to link information with application and system log data. Pearson uses this information for system administration and to identify problems, improve service, detect unauthorized access and fraudulent activity, prevent and respond to security incidents, appropriately scale computing resources and otherwise support and deliver this site and its services.

Cookies and Related Technologies

This site uses cookies and similar technologies to personalize content, measure traffic patterns, control security, track use and access of information on this site, and provide interest-based messages and advertising. Users can manage and block the use of cookies through their browser. Disabling or blocking certain cookies may limit the functionality of this site.

Do Not Track

This site currently does not respond to Do Not Track signals.


Pearson uses appropriate physical, administrative and technical security measures to protect personal information from unauthorized access, use and disclosure.


This site is not directed to children under the age of 13.


Pearson may send or direct marketing communications to users, provided that

  • Pearson will not use personal information collected or processed as a K-12 school service provider for the purpose of directed or targeted advertising.
  • Such marketing is consistent with applicable law and Pearson's legal obligations.
  • Pearson will not knowingly direct or send marketing communications to an individual who has expressed a preference not to receive marketing.
  • Where required by applicable law, express or implied consent to marketing exists and has not been withdrawn.

Pearson may provide personal information to a third party service provider on a restricted basis to provide marketing solely on behalf of Pearson or an affiliate or customer for whom Pearson is a service provider. Marketing preferences may be changed at any time.

Correcting/Updating Personal Information

If a user's personally identifiable information changes (such as your postal address or email address), we provide a way to correct or update that user's personal data provided to us. This can be done on the Account page. If a user no longer desires our service and desires to delete his or her account, please contact us at customer-service@informit.com and we will process the deletion of a user's account.


Users can always make an informed choice as to whether they should proceed with certain services offered by InformIT. If you choose to remove yourself from our mailing list(s) simply visit the following page and uncheck any communication you no longer want to receive: www.informit.com/u.aspx.

Sale of Personal Information

Pearson does not rent or sell personal information in exchange for any payment of money.

While Pearson does not sell personal information, as defined in Nevada law, Nevada residents may email a request for no sale of their personal information to NevadaDesignatedRequest@pearson.com.

Supplemental Privacy Statement for California Residents

California residents should read our Supplemental privacy statement for California residents in conjunction with this Privacy Notice. The Supplemental privacy statement for California residents explains Pearson's commitment to comply with California law and applies to personal information of California residents collected in connection with this site and the Services.

Sharing and Disclosure

Pearson may disclose personal information, as follows:

  • As required by law.
  • With the consent of the individual (or their parent, if the individual is a minor)
  • In response to a subpoena, court order or legal process, to the extent permitted or required by law
  • To protect the security and safety of individuals, data, assets and systems, consistent with applicable law
  • In connection the sale, joint venture or other transfer of some or all of its company or assets, subject to the provisions of this Privacy Notice
  • To investigate or address actual or suspected fraud or other illegal activities
  • To exercise its legal rights, including enforcement of the Terms of Use for this site or another contract
  • To affiliated Pearson companies and other companies and organizations who perform work for Pearson and are obligated to protect the privacy of personal information consistent with this Privacy Notice
  • To a school, organization, company or government agency, where Pearson collects or processes the personal information in a school setting or on behalf of such organization, company or government agency.


This web site contains links to other sites. Please be aware that we are not responsible for the privacy practices of such other sites. We encourage our users to be aware when they leave our site and to read the privacy statements of each and every web site that collects Personal Information. This privacy statement applies solely to information collected by this web site.

Requests and Contact

Please contact us about this Privacy Notice or if you have any requests or questions relating to the privacy of your personal information.

Changes to this Privacy Notice

We may revise this Privacy Notice through an updated posting. We will identify the effective date of the revision in the posting. Often, updates are made to provide greater clarity or to comply with changes in regulatory requirements. If the updates involve material changes to the collection, protection, use or disclosure of Personal Information, Pearson will provide notice of the change through a conspicuous notice on this site or other appropriate way. Continued use of the site after the effective date of a posted revision evidences acceptance. Please contact us if you have questions or concerns about the Privacy Notice or any objection to any revisions.

Last Update: November 17, 2020