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Booting Up

Booting Up. first 64K computer address space. read-only. non-volatile. RAM. 0 8K 16K 24K 32K 40K 48K 56K 64K. EEPROM (contains code). battery-backed RAM (contains hardware settings). what is in a PC’s memory when the computer is off?

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Booting Up

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  1. Booting Up boot.ppt

  2. first 64K computer address space read-only non-volatile RAM 0 8K 16K 24K 32K 40K 48K 56K 64K EEPROM(contains code) battery-backed RAM(contains hardware settings) • what is in a PC’s memory when the computer is off? • most of RAM is empty when the PC first powers up • RAM is volatilebecause its contents are lost when power goes off • but, two small parts are different • when the PC first powers up, where is the operating system? boot.ppt

  3. battery-backed RAM RAM 0 8K 16K 24K 32K 40K 48K 56K 64K EEPROM(contains code) battery-backed RAM(contains hardware settings) • battery-backed RAM contains a simple database • also called the CMOS • a program called “Setup” is used to modify it • you can start Setup only while booting the computer • its data describes hardware parameters • time/date • what disk drives are present • what kind of display is present • how much memory is present • how fast some components should run • etc. • how does the configuration data get modified? • plug and play devices • the Setup program boot.ppt

  4. the EEPROM RAM 0 8K 16K 24K 32K 40K 48K 56K 64K EEPROM(contains code) battery-backed RAM(contains hardware settings) • the EEPROM contains the programs needed to start the computer • also called the BIOS, or the firmware • because it contains only programs, it can be read-only: • BIOS routines (a minimal keyboard/display driver) • POST routines (e.g., RAM parity check, keyboard test) • setup program – lets users view or modify hardware settings • bootstrap program – searches disk drives for an operating system • how does the BIOS get updated if its programs need to change? boot.ppt

  5. add-on boards also contain BIOS chips • the motherboard BIOS contains code to access the keyboard, floppy drive, ATA (IDE) hard disk controllers, USB devices, and disk drives • a computer system can contain several BIOS firmware chips • plug-in adapter cards such as network interface cards and video boards often include their own BIOS • complementing or replace the system BIOS code for the given component • CMOS (“Setup”) database maps these extra BIOS programs into the low memory address space boot.ppt

  6. what is a disk drive? • a piece of physical hardware • non-volatile storage • programs on a disk drive must be loaded into RAM before they execute • disk drives must be subdivided into partitions • the act of writing on a disk drive to partition it is called partitioning • you have to know which OS will use the partition before you create it • partitions have to be formatted with a particular file system • typically, each OS uses a different file system • PC partitions have one or more logical drive letters associated with them • Solaris partitions have directories associated with them (“mounted”) boot.ppt

  7. more about disk drives • what is fdisk? • a utility from Microsoft for partitioning disks • part of the original DOS 6.x operating system • a more versatile utility: Partition Magic • what is a boot sector? (master boot record, or MBR) • the first accessible “sector” on a drive • it contains: • a table of (up to 4) partitions • optionally, code to bootstrap an OS from the “active” partition • the partition table in the boot sector contains up to 4 entries: • primarypartition • takes up one entry in partition table, and contains a single logical drive • extended partition • takes up 1 entry in partition table, and may contain multiple DOS, Linux or other partitions (logical drives in Windows) • Solaris partition • takes up 1 entry in partition table • activepartition • a primary partition that is bootable boot.ppt

  8. starting Windows on an x86-based computer • since 1981, all x86-based computers use the partition style known as the master boot record (MBR) • first used by MS-DOS in 1981, and continued up through Windows XP Pro • when you start your computer, the first code that executes is the BIOS • BIOS loads the bytes from the MBR of the boot device into memory • it then transfers control to the bytes just loaded into memory • the MBR’s first bytes are code to start loading the operating system • but first, it has to find the operating system • It looks that up in the partition table (stored in the end of the MBR) • Because MBR is the only partition style available on x86-based computers running Windows XP or earlier, it is used automatically and you do not need to choose this style • Dynamic disks were introduced in Windows 2000 and they provide features that basic disks do not, such as the ability to create volumes that span multiple disks, including fault-tolerant mirrored and RAID-5 volumes. • Requires a GPT partition style • GPT stands for “GUID Partition Table” • GUID stands for “Globally Unique ID” boot.ppt

  9. MBR • the first physical sector on a disk contains a data structure known as the Master Boot Record (MBR). The MBR contains the following: • a boot program (up to 442 bytes in size) • a disk signature (a unique 4-byte number) • a partition table (up to four entries) • an end-of-MBR marker (always 0x55AA) boot.ppt

  10. enter GPT partitions and EFI • Extensible Firmware Interface (EFI) is a specification that defines a software interface between an operating system and platform firmware. • EFI is intended as a significantly improved replacement of the old legacy BIOS firmware interface historically used by all IBM PC compatible personal computers • the EFI specification was originally developed by Intel • now managed by the Unified EFI Forum and is officially known as Unified EFI (UEFI) • Used first on Itanium processor systems • Also used by 64-bit Windows versions • Vista can use them as data disks (but not boot drives) • XP Pro cannot use them at all boot.ppt

  11. kinds of hard drives today • basic MBR disk – Windows XP systems all use this • basic GPT disk • dynamic MBR disk • dynamic GPT disk • if using EFI, there also has to be a special partition containing the particular EFI code your computer system happens to need • what are the implications of this? boot.ppt

  12. Boot Camp • I have a MacBook capable of running both Mac OS X and Windows XP • the laptop is 2 years old • cost was $1200 + $300 for Windows XP Pro license • it only has Mac OS 10.4, “Tiger” • not 10.5, “Leopard”, the latest • came with 512K, not enough memory to run Leopard • how did I get it to run Windows? • Mac OS 10.4 let me download a special program called Boot Camp • it created a Windows partition, after which, I installed Windows XP Pro on that partition • coupla years went by… • recently, my Windows XP install partition got sick; I needed to restart Windows • it died in a way that even Mac OS X was unable to redo the Windows partition • so I also had to reinstall Mac OS X (10.4) • Boot Camp was cripple-ware • “expired”; could no longer download it • what to do? boot.ppt

  13. the end of this slideset boot.ppt

  14. I have a MacBook with Apple’s “Boot Camp” program on it • What does Boot Camp do? • Can I just run Windows on my MacBook without boot.ppt

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