Wikipedia
EFUSE
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.