Reset vector

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.

• 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 IP 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)