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In computing, eFuse is a technology invented by IBM which allows for the dynamic real-time reprogramming of computer chips. In the abstract, 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 Xbox 360's bootloaders, for instance, will check the number of burnt fuses before attempting to install new firmware. The number 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), then the bootloader will prevent installation of the older firmware. After successfully installing a new firmware version, the system will burn the required number of fuses to prevent downgrading. This feature is also seen in the Nintendo Switch.
- 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
- NVidia Tegra X1 SoC used in the Nintendo Switch hybrid video game console.
- Samsung Knox devices detect if a non-Samsung boot path has ever run.
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