Reset vector
Encyclopedia
Reset vector is a computing
term used to describe the default location a central processing unit
will go to find the first instruction it will execute after a reset. That is to say, the reset vector is a pointer or address
where the CPU should always begin as soon as it is able to execute instructions.
Computing
Computing is usually defined as the activity of using and improving computer hardware and software. It is the computer-specific part of information technology...
term used to describe the default location a central processing unit
Central processing unit
The central processing unit is the portion of a computer system that carries out the instructions of a computer program, to perform the basic arithmetical, logical, and input/output operations of the system. The CPU plays a role somewhat analogous to the brain in the computer. The term has been in...
will go to find the first instruction it will execute after a reset. That is to say, the reset vector is a pointer or address
Memory address
A digital computer's memory, more specifically main memory, consists of many memory locations, each having a memory address, a number, analogous to a street address, at which computer programs store and retrieve, machine code or data. Most application programs do not directly read and write to...
where the CPU should always begin as soon as it is able to execute instructions.
- The reset vector for the 80386DX and later x86 processors is 0xFFFF0, although the value of the CS register at reset is 0xF000 and the value of the IPProgram counterThe program counter , commonly called the instruction pointer in Intel x86 microprocessors, and sometimes called the instruction address register, or just part of the instruction sequencer in some computers, is a processor register that indicates where the computer is in its instruction sequence...
register at reset is 0xFFF0. In actuality, current x86 processors fetch from the physical address 0xFFFFFFF0. This is due to a hidden base address portion of the CS register in real mode which defaults to 0xFFFF0000 after reset.
- The reset vector for the 8086 processor is at address FFFF:0000
- The reset vector for the 80286 processor is at address 0x00FFFFF0 (just below 16Mb)