8086 µProcessor | Proteus Simulation | 7 Segment & Stepper Motor
The 8086 starts execution at 0xFFFF:0000, which is only 16 bytes before end of address space.
You as a developer are supposed to put a jump instruction there to point the program counter at the actual program start.
If the PC just continues incrementing, you get a wrap-around at FFFF:0010. The behaviour here differes between chip versions, the original 8086 wraps to 0000:0000, while modern variants (80286 and up) would access memory beyond 1MB. See also &quot;A20 gate&quot;.
In most cases using addresses bigger than FFFF:000F will be a bug. Don't do that.