Overclocking suite AMD OverDrive can't increase a "locked" CPU's multiplier value. When OverDrive encounters a locked CPU, it allows the user only to decrease the multiplier's value below the factory settings, whereas unlocked CPUs can be adjusted in both directions. OverDrive is unable to override the locked hardware settings on locked processors; however, CPUs with locked multipliers can still be overclocked despite the locked nature of the chip making the process less versatile.
A CPU's speed is determined by the product of the CPU multiplier and the motherboard's Front Side Bus reference clock. The FSB measures how quickly the CPU can communicate with the system memory. The term "overclocking" refers to increasing the CPU speed by adjusting the multiplier, FSB reference clock or voltage. The term "underclocking" refers to reverse overclock adjustments to decrease the CPU speed. Overclocking pushes more performance out of the same hardware at the expense of producing extra heat and risking hardware damage. In contrast, underclocking slows down the system to either produce less heat to avoid heat damage or run older software that the CPU's native speed is too fast for.
Locked and Unlocked
The ability to adjust the FSB and voltage settings rest on the motherboard, but the CPU itself has the final say on if the multiplier value can be adjusted. A locked CPU disables the user from increasing the CPU's multiplier above factory defaults whereas an unlocked CPU allows the user to change the multiplier value at will. CPU manufacturers can lock a CPU to specifically prevent users from being able to overclock it and get better performance without paying for a faster CPU -- especially when the CPU runs cool at its default settings.
AMD OverDrive is a software suite that lets a computer user manually adjust the CPU clock speed within the operating system. OverDrive can adjust the CPU multiplier and FSB speed on the fly with graphical sliders. Before programs like OverDrive, unlocked CPUs could only be adjusted in the system's Basic Input Output Settings or through physically altering the motherboard. OverDrive is designed to streamline the overclocking process, letting the user stability test clock speed adjustments without having to reboot the computer between each performance uptick. Safe overclocking is a gradual process: the user will only adjust the CPU multiplier by a single value or adjust the FSB by 10 MHz or fewer between stability tests.
Locked AMD Processors
OverDrive changes its accessible options depending on what the computer's specific CPU model allows. Locked AMD processors will still show "Clock" adjustment settings on the "Clock/Voltage" menu, but display the the sliders all the way to the right, bearing the maximum and default multiplier value. The menu will still show any operational clock adjustment options. Even though locked processors restrict clock adjustment options, you can still increase values to the point where the system crashes from instability or can overheat and break the CPU.
- Tom's Hardware Reviews: Making Lemonade: Overclocking Your Locked AMD Processor
- AMD Downloads: AMD OverDrive
- PCWorld: AMD OverDrive Easily Overclock an AMD Rig
- PCMag.com: Encyclopedia: Definition of: Overclock
- EnthusiastPC: Overclocking Basics (CPU)
- Computer Hope Multiplier
- Computer Hope: FSB
- PCWorld: Overclocking for Newbies
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