Initial BIOS load for a personal computer system

We claim:

1. An apparatus for loading an operational interface into a personal computer system, the personal computer system including a system processor and a random access memory electrically coupled thereto, said apparatus comprising:

a direct access storage device being electrically coupled to the system processor, said direct access storage device being capable of storing a plurality of data records;

a master boot record stored on the direct access storage device, said master boot recording including an executable code segment;

a read only memory being electrically coupled to the system processor;

a first portion of the operational interface stored in the read only memory starting at a particular address, said first portion of the operational interface initializing the system and the direct access storage device to load in said master boot record into random access memory; and

a remaining portion of the operational interface stored on the direct access storage device, wherein the first portion of the operational interface transfers control to the executable code segment of the master boot record in order to effect the loading of the remaining portion of the operational interface into the random access memory, said remaining portion of the operational interface being stored starting at said particular address and superseding the first portion of the operational interface and initializing the rest of the personal computer system in order to load in an operating system to begin operation of the personal computer system.

2. The apparatus of claim 1, wherein the direct access storage device comprises a fixed disk.

3. The apparatus of claim 1, wherein the direct access storage device comprises a diskette.

4. The apparatus of claim 1, wherein the master boot record further includes a data segment, the data segment representing a hardware configuration of the personal computer system which is compatible with said master boot record, and further wherein the read only memory includes data representing a hardware configuration of the system processor, wherein before said remaining portion of the operational interface is loaded into random access memory, said first portion of the operational interface compares the hardware configuration data from the master boot record with the hardware configuration data from the read only memory to verify the master boot record is compatible with the system processor.

5. The apparatus of claim 4, wherein the data segment of the master boot record includes a value representing a system planar which is compatible with the master boot record and further wherein the system planar further includes a means for uniquely identifying the system planar in order to verify that the master boot record is compatible to the system planar.

6. The apparatus of claim 4, wherein the hardware configuration data on the master boot record includes a model value and a submodel value, wherein the model value identifies a system processor which is compatible with said master boot record and the submodel value represent an I/O configuration of a system planar which is compatible with the master boot record, and further wherein said read only memory includes a corresponding model value identifying the system processor and submodel value representing the I/O configuration of the system planar, wherein said model value and submodel value of the master boot record are compared to the corresponding model and submodel values of the read only memory respectively, in order to verify that the master boot record is compatible with the system processor and the I/O configuration of the system planar.

7. The apparatus of claim 6, wherein said first portion of the operational interface generates a first error to indicate the master boot record is not compatible with the system hardware.

8. The apparatus of claim 1, wherein the personal computer system further includes a nonvolatile random access memory being electrically coupled to the system processor, said nonvolatile random access memory including data representing the system configuration, said data being updated when the configuration of the system is changed, wherein said first portion of the operational interface compares said data in the nonvolatile random access memory to corresponding data in the read only memory to determine if the configuration of the system has changed.

9. The apparatus of claim 8, wherein said first portion of the operational interface generates a second error to indicate that the system configuration has changed.

10. The apparatus of claim 1, wherein said master boot record includes an identifying means to identify the record in order to distinguish the master boot from other records included on the direct access storage device.

11. The apparatus of claim 10, wherein said identifying means comprises a predetermined character code.

12. The apparatus of claim 11 wherein said predetermined code is prefactory to said code segment of the master boot record.

13. The apparatus of claim 10, wherein said master boot record includes a checksum value to verify the validity of the master boot record when loaded into the random access memory.

14. The apparatus of claim 1, wherein said remaining portion of the operational interface includes a checksum value to verify the validity of the remaining portion of the operational interface when loaded into the random access memory.

15. The apparatus of claim 1, wherein said master boot record includes a predetermined pattern, and further wherein said read only memory includes a corresponding predetermined pattern in order to verify that the first portion of the operational interface is included within a predefined read only memory.

16. The apparatus of claim 15, wherein said executable code segment generates an error to indicate that the read only memory is not compatible with the master boot record.

17. A personal computer system comprising:

a system processor;

a random access memory being the main memory and electrically coupled to the system processor;

a system planar board having a plurality of I/O slots being electrically coupled to the system processor,

a direct access storage device being electrically coupled to the system processor, the direct access storage device capable of storing a plurality of data records;

a master boot record included in the direct access storage device, the master boot record having a data segment and an executable code segment, the data segment representing a hardware configuration of the personal computer system which is compatible with said master boot record;

a read only memory being electrically coupled to the system processor, the read only memory having data representing a hardware configuration of the system;

a first portion of an operational interface being included in the read only memory, said first portion of the operational interface initializing the system and the direct access storage device to load in said master boot record, said first portion of the operational interface further comparing the hardware configuratin data from the master boot record to the hardware configuration data of the read only memory to verify the compatibility of the master boot record with the system processor;

a remaining portion of the operational interface being included in the direct access storage device, wherein after verifying the compatibility of the master boot record with the system processor, the first portion of the operational interface transfers control to the executable code segment of the master boot record in order to effect the loading of the remaining portion of the operational interface into the random access memory, said remaining portion of the operational interface superseding said first portion of the operational interface.

18. The apparatus of claim 17, wherein the data segment of the master boot record includes a value representing a system planar being compatible with the master boot record and further wherein the system planar further includes a means for uniquely identifying the system planar in order to verify the compatibility of the master boot record to the system planar.

19. The apparatus of claim 17, wherein the direct access storage device comprises a fixed disk.

20. The apparatus of claim 17, wherein the hardware configuration data on the master boot record includes a model value and a submodel value, wherein the model value identifies the system processor and the submodel value represent the I/O configuration of the system planar, said model value and submodel value being compared to corresponding values in the read only memory to verify the compatibility of the master boot record to the hardware configuration.

21. The apparatus of claim 17, wherein the personal computer system further includes a nonvolatile random access memory, said nonvolatile random access memory storing values representing the system configuration, said data being updated when the configuration of the system is changed, wherein said first portion of the operational interface compares said values in the nonvolatile random access memory to corresponding values in the read only memory to determine if the configuration of the system has changed.

22. An apparatus for loading an operational interface into a personal computer system, the personal computer system having a system processor being electrically coupled to a random access memory, said apparatus comprising:

a direct access storage device being electrically coupled to the system processor, the direct access storage device being capable of storing a plurality of data records;

a read only memory being electrically coupled to the system processor;

a first portion of the operational interface being included in the read only memory; and

a remaining portion of the operational interface being included in the direct access storage device, wherein the first portion of the operational interface initializes the system processor and direct storage device to effect load the remaining portion of the operational interface into random access memory, said remaining portion of the operational interface effectively superseding the first portion of the operational interface to assist in the operation of the system.

23. A method for loading an operational interface from a direct access storage device of a personal computer system, the personal computer system having a system processor electrically coupled to a system planar, the planar further being electrically coupled to a random access memory, a read only memory, and the direct access storage device, said method comprising the steps of:

(a) initializing the system with a first portion of the operational interface resident in the read only memory;

(b) initializing with the first portion of the operational interface the direct access storage device, the direct access storage device further having a master boot record and the remaining portion of the operational interface;

(c) loading with the first portion of the operational interface the master boot record into random access memory, the master boot record including a data segment and an executable code segment, the data segment having data representing the hardware of the system for which the remaining portion of the operational interface is compatible;

(d) verifying the compatibility of the master boot record with the system hardware by comparing the data representing the system hardware to corresponding compatibility data stored in the read only memory; and

(e) executing the code segment of the master boot record to load the remaining portion of the operational interface into the random access memory; and

(f) passing control to the remaining portion of the operational interface once it is loaded into random access memory.

24. The method of claim 23, wherein step (d) of verifying further includes the steps of:

(g) verifying that the master boot record is compatible with the planar by comparing a planar ID accessible by the system processor with a planar ID value stored in the data segment of the master boot record; and

(h) verifying that the master boot record is compatible with the system processor and I/O configuration of the planar by comparing respectively model and submodel values stored in the read only memory with model and submodel values stored in the data segment of the master boot record.

25. The method of claim 23, wherein the system further includes a nonvolatile memory being electrically coupled to the system processor, wherein the nonvolatile memory includes data representing the system configuration, said method further including the step of:

(i) comparing the data in nonvolatile random access memory to the data in read only memory to determine whether the system configuration has changed; and

(j) generating an indication that the system configuration has changed before loading the operational from the direct access storage device.

26. The method of claim 23, wherein step (c) of loading further includes the steps of:

(k) searching through a predetermined number of records on the direct access image device for a master boot record;

(1) identifying the master boot record with an identifying means included within the master boot record.

(m) loading the master boot record into random access memory upon locating the master boot record among the data records on the direct access storage device.

27. The method of claim 24, further including the step of validating successful load of the master boot record.

Description Submit all comments and votes

CROSS REFERENCE TO RELATED PATENT APPLICATIONS

The present patent application is one of a group of copending applications which concern the same overall computer system but which individually claim different inventive concepts embodied in such computer system. These related patent applications were filed on the same date, namely Aug. 25, 1989, are specifically incorporated by reference herein, and are more particularly described as follows:

(1) Application Ser. No. 07/399,631, entitled "An Apparatus and Method for Loading BIOS from a Diskette in a Personal Computer System", now abandoned the inventors being Bealkowski et al;

(2) Application Ser. No. 07/398,860, entitled "An Apparatus and Method for Decreasing the Memory Requirements for BIOS in a Personal Computer System", now U.S. Pat. No. 5,136713 the inventors being Bealkowski et al.; and

(3) Application Ser. No. 07/398,820, entitled "An Apparatus and Method for Preventing Unauthorized Access to BIOS in a Personal Computer System", now U.S. Pat. No. 5,022,077 the inventors being Bealkowski et al.

FIELD OF THE INVENTION

This invention relates to personal computer systems and in particular to a method and device for installing BIOS into a personal computer system.

BACKGROUND DISCUSSION

Personal computer systems in general and IBM personal computers in particular have attained widespread use for providing computer power to many segments of today's modern society. Personal computer systems can usually be defined as a desk top, floor standing, or portable microcomputer that consists of a system unit having a single system processor, a display monitor, a keyboard, one or more diskette drives, a fixed disk storage, and an optional printer. One of the distinguishing characteristics of these systems is the use of a motherboard or system planar to electrically connect these components together. These systems are designed primarily to give independent computing power to a single user and are inexpensively priced for purchase by individuals or small businesses. Examples of such personal computer systems are IBM's PERSONAL COMPUTER AT and IBM's PERSONAL SYSTEM/2 Models 25, 30, 50, 60, 70 and 80.

These systems can be classified into two general families. The first family, usually referred to as Family I Models, use a bus architecture exemplified by the IBM PERSONAL COMPUTER AT and other "IBM compatible" machines. The second family, referred to as Family II Models, use IBM's MICROCHANNEL bus architecture exemplified by IBM's PERSONAL SYSTEM/2 Models 50 through 80.

Beginning with the earliest personal computer system of the family I models, such as the IBM Personal Computer, it was recognized that software compatibility would be of utmost importance. In order to achieve this goal, an insulation layer of system resident code, also referred to as "microcode", was established between the hardware and software. This code provided an operational interface between a user's application program/operating system and the device to relieve the user of the concern about the characteristics of hardware devices. Eventually, the code developed into a BASIC input/output system (BIOS), for allowing new devices to be added to the system, while insulating the application program from the peculiarities of the hardware. The importance of BIOS was immediately evident because it freed a device driver from depending on specific device hardware characteristics while providing the device driver with an intermediate interface to the device. Since BIOS was an integral part of the system and controlled the movement of data in and out of the system processor, it was resident on the system planar and was shipped to the user in a read only memory (ROM). For example, BIOS in the original IBM Personal Computer occupied 8K of ROM resident on the planar board.

As new models of the personal computer family were introduced, BIOS had to be updated and expanded to include new hardware and I/0 devices. As could be expected, BIOS started to increase in memory size. For example, with the introduction of the IBM PERSONAL COMPUTER AT, BIOS grew to require 32K bytes of ROM.

Today, with the development of new technology, personal computer systems of the Family II models are growing even more sophisticated and are being made available to consumers more frequently. Since the technology is rapidly changing and new I/O devices are being added to the personal computer systems, modification to the BIOS has become a significant problem in the development cycle of the personal computer system.

For instance, with the introduction of the IBM Personal System/2 with MICROCHANNEL architecture, a significantly new BIOS, known as advanced BIOS, or ABIOS, was developed. However, to maintain software compatibility, BIOS from the Family I models had to be included in the Family II models. The Family I BIOS became known as Compatibility BIOS or CBIOS. However, as previously explained with respect to the IBM PERSONAL COMPUTER AT, only 32K bytes of ROM were resident on the planar board. Fortunately, the system could be expanded to 96K bytes of ROM. Unfortunately, because of system constraints, this turned out to be the maximum capacity available for BIOS. Luckily, even with the addition of ABIOS, ABIOS and CBIOS could still squeeze into 96K of ROM. However, only a small percentage of the 96K ROM area remained available for expansion. With the addition of future I/O devices, CBIOS and ABIOS will eventually run out of ROM space. Thus, new I/O technology will not be able to be easily integrated within CBIOS and ABIOS.

Due to these problems, plus the desire to make modification in Family II BIOS as late as possible in the development cycle, it has become necessary to off load portions of BIOS from the ROM. Since marketability and consumer acceptance of personal computer systems appear to require the ability to add new I/O devices and to minimize cost, it should be appreciated that easy modification of Family II models' BIOS is a substantial factor in achieving success in accordance with this invention. Thus, there exists a need for developing a method and apparatus which permits portions of BIOS to be stored on a direct access storage device such as a fixed disk or on the diskette drive. These portions can then be easily modified and loaded into the personal computer system when required.

SUMMARY OF THE INVENTION

The present invention has been developed for the purpose of alleviating the above mentioned problems. Accordingly, the invention has as one of its objects an apparatus and method for increasing the number of devices BIOS supports by storing a portion of BIOS on a direct access storage device.

Another objective of the present invention is to provide an apparatus and method for loading BIOS from a direct access storage device into main memory.

Yet another objective of the present invention is to provide an apparatus and method which confirms the compatibility between BIOS and the personal computer system.

Another objective of the present invention is the ability to verify the system configuration before loading BIOS from the direct access storage device.

Broadly considered, a personal computer system according to the present invention comprises a system processor, a random access main memory, a read only memory, and at least one direct access storage device. The read only memory includes a first portion of BIOS. The first portion of BIOS initializes the system processor and the direct access storage device to read a master boot record from the direct access storage device into the random access memory.

The master boot record includes a data segment and an executable code segment. The data segment includes data representing system hardware and a system configuration which is supported by the master boot record. The first BIOS portion confirms the master boot record is compatible with the system hardware by verifying the data from the data segment of the master boot record agrees with data included within the first BIOS portion representing the system processor, system planar, and planar I/O configuration.

If the master boot record is compatible with the system hardware, the first BIOS portion vectors the system processor to execute the executable code segment of the master boot record. The executable code segment confirms that the system configuration has not changed and loads in the remaining BIOS portion from the direct access storage device into random access memory. The executable code segment then verifies the authenticity of the remaining BIOS portion and vectors the system processor to begin executing the BIOS now in random access memory. BIOS, executing in random access memory, then boots up the operating system to begin operation of the personal computer system. The first BIOS portion, being no longer addressable and superseded by the remaining BIOS portion, is abandoned.

BRIEF DESCRIPTION OF THE DRAWINGS

The foreground aspects and other features of the present invention are explained in the following written description, taken in connection with the accompanying drawings, wherein:

FIG. 1 illustrates a cut away view of a personal computer system showing a system planar board connected to a plurality of direct access storage devices;

FIG. 2 shows a system block diagram for the personal computer system of FIG. 1;

FIG. 3 is a memory map for the ROM BIOS included on the planar board;

FIG. 4 is a flowchart describing the overall process for loading a BIOS image from a direct access storage device;

FIG. 5 illustrates the record format for the master boot record;

FIG. 6A is a flowchart describing the operation of the IBL routine;

FIG. 6B is a flowchart showing the steps for loading a BIOS image from a fixed disk;

FIG. 6C is a flowchart showing the steps for loading the BIOS image from a diskette;

FIG. 6D is a flowchart showing greater detail in checking the compatibility between the master boot record and the planar/processor; and

FIG. 7 is a detailed flowchart showing the operation of the executable code segment of the master boot record.

DESCRIPTION OF A PREFERRED EMBODIMENT

The following detailed description is of the best presently contemplated mode for carrying out the invention. This description is not to be taken in a limiting sense but is made merely for the purpose of illustrating the general principles of the invention since the scope of the invention is best defined by the appending claims.

Referring now to the drawings, and in particular to FIG. 1, there is shown a cutaway version of a personal computer system 10, having a plurality of DASD (Direct Access Storage Devices) 12-16 connected to a system or planar board 24 through a plurality of I/O slots 18. A power supply 22 provides electrical power to the system 10 in a manner well known. The planar board 24 includes a system processor which operates under the control of computer instructions to input, process, and output information.

In use, the personal computer system 10 is designed primarily to give independent computing power to a small group of users or a single user and is inexpensively priced for purchase by individuals or small businesses. In operation, the system processor operates under an operating system, such as IBM's OS/2 Operating System or PC-DOS. This type of operating system includes a BIOS interface between the DASD 12-16 and the Operating System. A portion of BIOS divided into modules by function is stored in ROM on the planar 24 and hereinafter will be referred to as ROM-BIOS. BIOS provides an interface between the hardware and the operating system software to enable a programmer or user to program their machines without an indepth operating knowledge of a particular device. For example, a BIOS diskette module permits a programmer to program the diskette drive without an indepth knowledge of the diskette drive hardware. Thus, a number of diskette drives designed and manufactured by different companies can be used in the system. This not only lowers the cost of the system 10, but permits a user to choose from a number of diskette drives.

Prior to relating the above structure to the present invention, a summary of the operation in general of the personal computer system 10 may merit review. Referring to FIG. 2, there is shown a block diagram of the personal computer system 10. FIG. 2 illustrates components of the planar 24 and the connection of the planar 24 to the I/O slots 18 and other hardware of the personal computer system. Located on the planar 24 is the system processor 26 comprised of a microprocessor which is connected by a local bus 28 to a memory controller 30 which is further connected to a random access memory (RAM) 32. While any appropriate microprocessor can be used, one suitable microprocessor is the 80386 which is sold by Intel.

While the present invention is described hereinafter with particular reference to the system block diagram of FIG. 2, it is to be understood at the outset of the description which follows, it is contemplated that the apparatus and methods in accordance with the present invention may be used with other hardware configurations of the planar board. For example, the system processor could be an Intel 80286 or 80486 microprocessor.

Accessible by the processor is a planar identification number (planar ID). The planar ID is unique to the planar and identifies the type of planar being used. For example, the planar ID can be hardwired to be read through an I/O port of the system/processor 26 by using switches.

The local bus 28 is further connected through a bus controller 34 to a read only memory (ROM) 36 on the planar 24.

An additional nonvolatile memory (NVRAM) 58 is connected to the microprocessor 26 through a serial/parallel port interface 40 which is further connected to bus controller 34. The nonvolatile memory can be CMOS with battery backup to retain information whenever power is removed from the system. Since the ROM is normally resident on the planar, model and submodel values stored in ROM are used to identify the system processor and the system planar I/O configuration respectively. Thus these values will physically identify the processor and planar I/O configuration. The NVRAM is used to store system configuration data. That is, the NVRAM will contain values which describe the present configuration of the system. For example, NVRAM contains information describing the capacity of a fixed disk or diskette, the type of display, the amount of memory, time, date, etc. Additionally, the model and submodel values stored in ROM are copied to NVRAM whenever a special configuration program, such as SET Configuration, is executed. The purpose of the SET Configuration program is to store values characterizing the configuration of the system in NVRAM. Thus for a system that is configured properly, the model a