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The lock is to support synchronization between two writers and the counter is for indicating consistency in readers. In addition to updating the shared data, the writer increments the sequence number, both after acquiring the lock and before releasing the lock. Readers read the sequence number before and after reading the shared data.
The BIOS uses the boot devices set in Nonvolatile BIOS memory , or, in the earliest PCs, DIP switches. The BIOS checks each device in order to see if it is bootable by attempting to load the first sector (boot sector). If the sector cannot be read, the BIOS proceeds to the next device.
BIOS interrupt calls perform hardware control or I/O functions requested by a program, return system information to the program, or do both. A key element of the purpose of BIOS calls is abstraction - the BIOS calls perform generally defined functions, and the specific details of how those functions are executed on the particular hardware of the system are encapsulated in the BIOS and hidden ...
The BIOS Boot Specification (BBS) was developed by a consortium comprising Compaq, Intel and Phoenix Technologies to standardize the initialization sequence of Plug and Play (PnP) BIOS and Option ROMs. [3] This standard is supported by most post-2000 BIOSes. The standard presents the notion of a Boot Connection Vector (BCV) table and BCV ...
INT 13h is shorthand for BIOS interrupt call 13 hex, the 20th interrupt vector in an x86-based (IBM PC-descended) computer system.The BIOS typically sets up a real mode interrupt handler at this vector that provides sector-based hard disk and floppy disk read and write services using cylinder-head-sector (CHS) addressing.
Older, less common BIOS-bootable devices include floppy disk drives, Zip drives, and LS-120 drives. Typically, the system firmware (UEFI or BIOS) will allow the user to configure a boot order. If the boot order is set to "first, the DVD drive; second, the hard disk drive", then the firmware will try to boot from the DVD drive, and if this fails ...
[citation needed] [17] In some implementations, the opcode is emulated through BIOS as a halting sequence. [18] Many computers in the Intel Pentium line can be locked up by executing an invalid instruction (F00F C7C8), which causes the computer to lock up. This became known as the Pentium F00F bug.
The bootstrap sequence in the BIOS will load the first valid MBR that it finds into the computer's physical memory at address 0x7C00 to 0x7FFF. [31] The last instruction executed in the BIOS code will be a "jump" to that address in order to direct execution to the beginning of the MBR copy.