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United States Patent 19 11 Patent Number: 5,692,190 Williams (45) Date of Patent: Nov

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United States Patent 19 11 Patent Number: 5,692,190 Williams (45) Date of Patent: Nov USOO5692 190A United States Patent 19 11 Patent Number: 5,692,190 Williams (45) Date of Patent: Nov. 25, 1997 54 BIOS EMULATION OF A HARD FLE IMAGE 5,136,711 8/1992 Hugard et al. .......................... 395/700 ASA DSKETTE 5,418,918 5/1995 Vander Kamp et al. .............. 395/700 5,432,935 7/1995 Kato et al. ................. ... 395/700 (75) Inventor: Donald D. Williams, Boca Raton, Fla. 5,459,867 10/1995 Adams et al. .......................... 395/700 5,475,845 12/1995 Orton et al. ............................ 395/700 73) Assignee: International Business Machines Corporation, Armonk, N.Y. Primary Examiner-Alvin E. Oberley 21 Appl. No.: 313,709 Assistant Examiner-John O. Chavis 22 Fed: Sep. 27, 1994 Attorney, Agent, or Firm-Bernard D. Bogdon 30 Foreign Application Priority Data 57 ABSTRACT Mar. 31, 1994 FR France .............................. 94 O3861 A personal computer is BIOS configured to boot from an 51 Int, C. r. G06F9445 installed CD-ROM having at least one bootable partition. To 52 U.S. Cl. ......................................................... 395/652 enable swapping of large amounts of data stored on the CD-ROM at the BIOS level after the initial boot, the 58 Field of Search .................................. 395/650, 700, DOS-BIOS interface is modified so that a CD-ROM emu 395/652 lated as a hard drive file will emulate a floppy diskette 56 References Cited image, a medium permitted by the operating system to be changed following an initial boot. U.S. PATENT DOCUMENTS 5,018,095 5/1991 Nissimov ................................ 395.404 7 Claims, 12 Drawing Sheets RESERVED EMUAE NO HARLEAS SC966 FLOPPY DESCRIPTORS e BOO CAAOG OFFSEEMUAE SAROBOOFRCR) YES PERSECTOR SECTORS PERAU SET BOOT DRIVE NUMBER OF FAS sEMUAEDRVE NUMBER OF DIRENTS NUMBERSECTORS MEDADESCRPOR SECTORS/FA NUMBER HEADS HDDENSECTORS BOOT DRIVE BCO HEAD SERIA NUMBER MORE THAN255 OS DRENTRIES NCORREC 2 2 SE CORRECORENRIES READDOS BPBSENGS EMULATION CORRECT U.S. Patent Nov. 25, 1997 Sheet 1 of 12 5,692,190 FIG. RESERMED SO9660 DESCRIPTORS HARDFILE \ U.S. Patent Nov. 25, 1997 Sheet 3 of 12 5,692,190 FIG, 3 U.S. Patent 5,692,190 S N 5 2 T?||@: @ st as a HistO 01 U.S. Patent Nov. 25, 1997 Sheet S of 12 5,692,190 FIG. 5 BIOSEBDA APPLICATIONS OR FREE SPACE U.S. Patent Nov. 25, 1997 Sheet 6 of 12 5,692,190 FIG, 6 BOSROM VIDEO RAM BOSEBDA APPLICATIONS OR FREE SPACE BIOSDATA AREA U.S. Patent Nov. 25, 1997 Sheet 7 of 12 5,692,190 FIG, 7 BIOSEBDA APPLICATIONS OR FREE SPACE BOSDATA AREA U.S. Patent Nov. 25, 1997 Sheet 8 of 12 5,692,190 FIG, 8 EMULATIONTABLE #4 to Bios 21 A DRME Cl BECOMES B: DRME C: - - - - - - - - - - - U.S. Patent Nov. 25, 1997 Sheet 9 of 12 5,692,190 FIG. 9 INFORMATION CH INFORMATION CD-DATABUFFER EMULATIONTABLE 4 EMULATIONABLE #3 EMUAONTABLE 2 EMUAEA A DRME : BECOMES : B: DRME NFORMATION U.S. Patent Nov. 25, 1997 Sheet 10 of 12 5,692,190 FIG. O CD-DAABUFFER to 2 21 Bigsa ea is a m at U.S. Patent Nov. 25, 1997 Sheet 11 of 12 5,692,190 FIG, SO9660 DESCRIPTORS BOO CAAOG PARTONTABLE BYTES PERSECTOR SECTORS PERAU NUMBER OF FAS BOO RECORD NUMBER OF DIRENTS NUMBERSECTORS FA MEDIADESCRIPTOR SECTORS/FAT FA-2 NUMBER HEADS HIDDEN SECTORS DIRECTORY BOOT DRIVE BOOTHEAD SERAL NUMBER U.S. Patent Nov. 25, 1997 Sheet 12 of 12 5,692,190 RESERVED EMULATE NO HARD FILEAS ISO9660 FIG, 12 FLOPPY DESCRIPTORS 2 BOOT CATALOG OFFSET EMULATE START TO BOOT RCRD PARTONTABLE CHANGEMEDIA TYPE TO FOh SET HIDDEN BOO RECORD SECTORS = O FA BYTES PERSECTOR SECTORS PERAU SE BOOTDRIVE NUMBER OF FATS - EMULATEDRIVE NUMBER OF DIRENTS DIRECTORY NUMBERSECTORS MEDIA DESCRIPTOR BOOTH SECTORS/FAT s E. E. NUMBER HEADS HIDDEN SECTORS BOOT DRIVE BOO HEAD READ BOS SERIAL NUMBER BPB MORE THAN 255 DOS DIRENTRIES NCORREC 2 2 SE CORRECT DIRENTRIES READ DOS BPBSETTINGS EMULATION CORREC 5,692,190 1. 2 BOS EMULATION OF A HARD FLE MAGE information, found in the same location on every formatted ASA DSKETTE disk, constitutes the DOS boot record. The BIOS then passes control to the boot record which instructs the PC on how to CROSS-REFERENCES TO RELATED load the two hidden operating system files to RAM (the files APPLICATIONS named BMIBIO.COM and BMDOS.COM on IBM The subject matter presented herein relates to inventions computers). After loading other operating system files into described in the following patent documents, all filed on RAM to carry out the rest of the boot up sequence, the boot even date and under common ownership herewith: Williams record is no longer needed. et al., BIOS DYNAMIC EMULATION OF MULTIPLE The root directory of the boot disk is next searched for a DISKETTES FROM A SINGLE MEDA, U.S. Ser. No. file created by the user (CONFIG.SYS) and which contains 08/313,710; Williams, DATA PROCESSOR HAVING commands instructing the operating system how to handle BIOS DECRYPTION OF EMULATED MEDIA IMAGES, certain operations such as how many files may be opened at U.S. Ser. No. 08/312,798; and Williams et al., BIOS EMU a time, and so-called device drivers which describe the LATION PARAMETER PRESERVATION ACROSS COM existence and characteristics of hardware devices not rec PUTER BOOTSTRAPPING, U.S. Ser. No. 08/312,149. 15 ognized by BIOS that may be connected to the PC. Notice: C Copyright, International Business Machines Cor Next loaded from the boot disk into RAM is the file poration 1994: A portion of the Disclosure of this patent COMMAND.COM which is an operating system file document contains material which is subject to copyright containing, among other functions, fundamental DOS com protection. The copyright owner has no objection to fac mands used throughout application program execution, and simile reproduction by anyone of the patent document or the a file named AUTOEXEC.BAT created by the user and patent disclosure, as it appears in the U.S. Patent and containing a series of DOS batch file commands or program Trademark Office, patent file or records, but otherwise names to be executed by the PC each time the computer is reserves all rights in its copyright whatsoever. turned on. This completes the boot up sequence, and at this point the computer is considered fully booted and ready to BACKGROUND OF THE INVENTION 25 be used. 1. Field of the Invention The usual types of storage media, in order of storage This invention relates generally to the bootstrapping density, are floppy disk and hard disk storage, which are sequence of a data processing system, such as a personal magnetic media, and more recently, CD-ROM which is an computer, and more particularly, to booting from a optical medium capable of storing a considerable amount of data. A CD-ROM is a “read only” medium, although CD-ROM. magneto-optical media, capable of being written to as well 2. Description of Related Art and Basis for Invention as read from, are emerging. Presently, floppy disks are 5.25 All computers, such as the various models of personal or 3.5 inches in diameter, with smaller sizes now emerging, computers, or PC's, produced by IBM Corporation, execute and are capable of storing up to 2.88 megabytes of data. "operating system software" that instructs the PC on how to 35 Hard disks store considerably more data, currently in the use other programs, termed "application software," such as range of up to 2 gigabits, arranged as clusters disbursed word processing and spreadsheet programs. Examples of PC throughout the medium. operating systems include MS-DOS and WINDOWS, CD-ROM's have attributes of both hard disks and floppy manufactured by Microsoft Corporation, and IBM's OS/2. diskettes, that is, they have the storage capacity of a hard Before a PC can run an operating system, it must load the drive and the replaceability of a diskette. CD-ROM tech operating system from a disk to the PC's working memory nology currently is capable of storing more than 600 mega which is ordinarily random access semiconductor memory bytes of read-only data along a continuous spiral track on a (RAM). This is carried out through a process known as phonograph record-like optical medium. As with other disk "bootstrapping,” or more simply, "booting" the PC. Booting 45 media, the CD divides its capacity into short segments, or occurs automatically when the PC is first turned on by a "large frames" for addressing. The number of such large process called a "cold boot," or by the user while the frames varies but can reach about 315,000, each containing computer is running ("warm boot"). 2352 bytes under a defined media standard. Most of the Bootstrapping performs only two functions, the first being frame contains data and the remainder is divided among a to run a power-on self-test, or POST, and the other to search 50 synchronization field, sector address tag field and an auxil the storage media (floppy diskette or hard disk) for the iary field. Data stored on the CD-ROM is formatted as operating system it will load. These functions are controlled sectors of data comprising 800 h bytes each, and with boot by firmware stored in one or more basic input-output system, record residing at a prescribed (11 h) sector in the last or BIOS, chips inside the PC. session on the CD. The boot record points to a boot catalog The POST initializes all the internal hardware and hard 55 providing descriptions and locations of disk or diskette ware connected to the PC known to it, such as memory, and image emulations recorded on the CD-ROM, one or more of tests and places the hardware in an operational state.
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