Hardware reset
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A hardware reset or hard reset of a
Hardware resets are an essential part of the
User initiated hard resets can be used to reset the device if the software hangs, crashes, or is otherwise unresponsive. However, data may become corrupted if this occurs.[1] Generally, a hard reset is initiated by pressing a dedicated reset button, or holding a combination of buttons on some mobile devices.[2][3] Devices may not have a dedicated Reset button, but have the user hold the power button to cut power, which the user can then turn the computer back on.[4] On some systems (e.g, the PlayStation 2 video game console), pressing and releasing the power button initiates a hard reset, and holding the button turns the system off.
Hardware reset in 80x86 IBM PC
The
Register | Value |
---|---|
CS (Code Segment) | 0xFFFF |
DS (Data Segment) | 0x0000 |
ES (Extra Data Segment) | 0x0000 |
SS (Stack Segment) | 0x0000 |
IP ( Instruction Pointer ) |
0x0000 |
The CPU uses the values of CS and IP registers to find the location of the next instruction to execute. Location of next instruction is calculated using this simple equation:
Location of next instruction = (CS<<4) + (IP)
This implies that after the hardware reset, the CPU will start execution at the physical address 0xFFFF0. In IBM PC compatible computers, This address maps to BIOS ROM. The memory word at 0xFFFF0 usually contains a JMP instruction that redirects the CPU to execute the initialization code of BIOS. This JMP instruction is absolutely the first instruction executed after the reset.[5]
Hardware reset in later x86 CPUs
Later x86 processors reset the CS and IP registers similarly, refer to Reset vector.
See also
- Power-on reset
- Power-on self test
- Reset vector
- Reboot (computing)
References
- ^ Fredman, Josh. "Can a Forced Shutdown Ruin My Computer?". smallbusiness.chron.com. Retrieved 2019-12-13.
- ^ "How to Hard Reset or Reboot any Android phone or tablet". trendblog.net. 2015-07-20. Retrieved 2019-12-13.
- ^ "How to Force Restart the iPhone X When It's Acting Up". Gadget Hacks. 14 September 2017. Retrieved 2019-12-13.
- ^ "What is a Reset Button?". www.computerhope.com. Retrieved 2019-12-13.
- ^ The 80x86 IBM PC and Compatible Computers (Volumes I & II (4th Edition)), By Mohamed Ali Mazidi and Janice Gillispie Mazidi, Section 9.1, Page 241.