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In computing, eFuse is a technology invented by IBM which allows for the dynamic real-time reprogramming of computer chips. Speaking abstractly, computer logic is generally "etched" or "hard-coded" onto a chip and cannot be changed after the chip has finished being manufactured. By utilizing a set of eFuses, a chip manufacturer can allow for the circuits on a chip to change while it is in operation.
The primary application of this technology is to provide in-chip performance tuning. If certain sub-systems fail, or are taking too long to respond, or are consuming too much power, the chip can instantly change its behavior by "blowing" an eFUSE.
Another use is to prevent downgrading the firmware of a device. The Nintendo Switch and Xbox 360's bootloaders for instance will check the amount of burned fuses before attempting to install new firmware. The amount of fuses expected to be burnt depends on the hardware model and the firmware to be installed. If too many fuses are burnt (meaning the firmware to be installed is older than the current firmware) the bootloader will panic, preventing installation. After successfully installing a new firmware version, the system will burn the required amount of fuses to match the new expected amount.
- IBM POWER5 and POWER6 high-end RISC processors
- IBM System z9 and System z10 mainframe processors
- Sony/Toshiba/IBM Cell used in PlayStation 3
- IBM/Microsoft Xenon CPU in the Xbox 360 game console.
- In the Nintendo Switch's bootloader 
- TI OMAP3-based mobile phones and other devices
- Samsung KNOX-enabled devices (KNOX warranty void bit)
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