E AP-608 APPLICATION NOTE Implementing a Plug and Play BIOS Using Intel's Boot Block Flash Memory CHARLES A. ANYIMI TECHNICAL MARKETING ENGINEER February 1995 Order Number: 292161-001 Information in this document is provided solely to enable use of Intel products. Intel assumes no liability whatsoever, including infringement of any patent or copyright, for sale and use of Intel products except as provided in Intel's Terms and Conditions of Sale for such products. Intel Corporation makes no warranty for the use of its products and assumes no responsibility for any errors which may appear in this document nor does it make a commitment to update the information contained herein. Intel retains the right to make changes to these specifications at any time, without notice. Contact your local Intel sales office or your distributor to obtain the latest specifications before placing your product order. MDS is an ordering code only and is not used as a product name or trademark of Intel Corporation. Intel Corporation and Intel's FASTPATH are not affiliated with Kinetics, a division of Excelan, Inc. or its FASTPATH trademark or products. *Other brands and names are the property of their respective owners. Additional copies of this document or other Intel literature may be obtained from: Intel Corporation Literature Sales P.O. Box 7641 Mt. Prospect, IL 60056-7641 or call 1-800-879-4683 © INTEL CORPORATION 1995 CG-041493 E AP-608 1.0 INTRODUCTION This application note provides a methodology for implementing a flash memory PnP BIOS using Intel’s Today’s PC can perform a myriad of functions, perhaps boot block flash. Emphasis is placed on PnP far more than the original designers of the PC ever requirements, hardware, and software considerations. envisioned. The number of software packages available Section 2 discusses the current BIOS paradigm and its for mass consumption is staggering, and more are being future. Section 3 provides an understanding of the Plug unveiled each year. Multimedia has enabled the PC to and Play architecture. Section 4 gives a high-level invade every nook and cranny of the home. The number overview of the boot block products. Section 5 discusses of systems being purchased with CD-ROMS, sound implementation while Section 6 looks at alternative cards, and graphics accelerators is growing at a solutions. phenomenal rate. The demand for additional hardware has led to an unprecedented craze for add-in cards and peripherals. While all this growth has been a tremendous 2.0 BENEFITS OF A PnP BOOT boon, it has had its downside as well. The PC has become BLOCK FLASH BIOS so sophisticated that new bus structures have been defined, new protocols have been introduced and new Perhaps you are wondering why flash is the medium of system configurations have emerged. All these changes choice advocated in this application note as the means have made an already complex tool more difficult to use for storing system BIOS, particularly for Plug and Play? by the PC user. From a PC user’s perspective, a PnP flash BIOS enables users to install new hardware without having to call the With the advent of Plug and Play (PnP), it seems a support number. This translates to ease-of-use: solution is in sight. Simply put, Plug and Play is a way of adding new features to a system without the usual · Easily updatable code assuring optimal BIOS headaches—like reconfiguring switches and jumpers, performance updating system configuration files, or other frustrating things. PnP enables a system to automatically configure · No need to edit the CONFIG.SYS file. system components, peripherals, and add-in devices just · No need to determine system type and match, prior to boot time. The basic input/output system (BIOS) somehow, to jumper settings. of PnP is responsible for the majority of the auto- configuration of the system. · No need to investigate available system resources and muddle through reassigning them. With its previous history of changes and the obvious · No need to fiddle with system memory reallocation. future changes that will take place as a result of PnP, it only makes sense to store the BIOS on a medium that · No need to buy a new system every time something allows the most flexible means of updating, while changes (increases system’s useful lifespan). maintaining a high level of reliability. Of course, all this has to be accomplished without adding to system costs or Plug and Play can make the usual experience of adding making it more difficult for PC users to get their work new functionality to an existing system as easy as: done. A PnP BIOS based on Intel’s boot block flash meets all of these demands and more. The PnP 1. Turn the system off. Specification, for instance, requires nonvolatile storage 2. Insert the new device. for old bus standards; the parameter blocks of the boot 3. Turn the system on. block flash were designed for such a function. As far as recovery code is concerned, the hardware-lockable boot PnP flash BIOS can also extend the life of the PC. By block area of the boot block flash memory provides enabling simple updates to the BIOS (simply insert the unparalleled data protection and guarantees system upgrade disk and the software programs the new BIOS), recovery. The inherent updateability of the boot block the user can get more out of their PC investment. flash memory, while in-system, reduces cost by supporting easy code changes and eliminating sockets. 1 AP-608 E From an OEM or system manufacturer’s standpoint, a elementary, few people understood it (or needed to). PnP flash BIOS enables the following benefits: Since that time, the PC BIOS has continued to evolve in order to accommodate the growing needs of the PC user. · Decreases overall technical support cost · Eliminates the need for excessive EPROM inventories. 2.1 The Old BIOS Paradigm · Reduces the need for sockets since flash can be In the original PC architecture, the BIOS code was fairly soldered onto the motherboard and updated in-system straightforward and required little memory space—about · Minimizes system chip count and system cost. 32 KB total. BIOS code provided the lowest-level of interface between the operating system and the hardware. · Reduces support costs. It was located at the top of memory for the 8088 system · Improves end-user perception of product (the original PC had a memory limit of upgradeability and ease-of-use. 1 MB). Even though only 32 KB were required, the PC designers knew the benefit of “breathing room” and, with When new features are added to the BIOS, a simple disk great foresight, reserved a total of 128 KB (from hex sent to the user or a connection to an on-line network is address E0000h to FFFFFh) for BIOS code storage, as all it takes for the user to achieve the upgrade. This has shown in Figure 1. When the AT was launched in 1984, one very important benefit for the OEM/manufacturer— its BIOS functions were extended by another it strengthens user faith in the product (and its 32 KB, thereby using half of the total BIOS space manufacturer) and enhances their perception of the available. product’s ease-of-use—which can be a great differentiator. Additionally, since each user no longer However, the introduction of BIOS created a crutch that needs to call the technical support line as often, this has been integrated into the PC: every new system costly overhead can be reduced, saving even more hardware component that was not already supported in money. the BIOS required a new BIOS to be generated, or at least an upgrade of the existing BIOS. This meant OEMs All these benefits are a result of the capabilities that a and system manufacturers needed to keep abundant flash PnP BIOS enables. Looking back to the original PC, quantities of ROMs and EPROMs handy to it was a fairly simple machine (by today’s standards) accommodate new BIOS versions. This was a with simple code designed to perform computational cumbersome and expensive solution, but it was soon math functions, database creation and management, and accepted as the norm. As long as the frequency of change word processing. Even though the BIOS code was to the BIOS remained minimal, this solution was adequate. 2 E AP-608 1 MB DOS Memory Map FFFFFh BIOS Code (64 KB) F0000h Additional 28F001B-T BIOS Space 28F002B-T E0000h (64 KB) Boot Block Flash Boot Block Flash Adapter and Boot Code Boot Code 16 KB 8 KB Graphic Space (256 KB) BIOS Parameters 8 KB 4 KB BIOS Parameters A0000h Configuration Utilities 8 KB 4 KB Configuration Utilities Additional BIOS ServiceS 96 KB Main BIOS Code, User Area 112 KB Runtime Services, (638.75 KB) Main BIOS Code, 128 KB Drivers, etc. Runtime Services, 00500h Drivers, etc. BIOS Data Area 00400h (256 Bytes) BIOS Stack Area 00300h (256 Bytes) Interrupt Vector Table (768 Bytes) 00000h 2161_01 Figure 1. Possible BIOS Segmentations Using Flash Components (1-Mbit or 2-Mbit) 2.2 Beyond the 128 KB Limit acquired more memory space either—but this would mean changing the architecture of the standard PC). Since then, BIOS code has undergone continual development, including the addition of custom features Today, PnP BIOS requirements may extend beyond to enhance system flexibility and more complex set-up 128 KB. A standard system BIOS consumes roughly routines. Today’s BIOS includes support for previously 64 KB; PnP support is another 12 KB; automatic power “advanced” features such as system configuration management support adds 2 to 10 KB; PCI (Peripheral analysis (diagnostics), power management, networking Components Interconnect) extensions hoard some capability and I/O support for devices with extremely 20 KB of the BIOS; and on-board VGA (Video Graphics high transfer rates.