IBM eFUSE

In computing, an eFuse (electronic fuse) is a microscopic fuse put into a computer chip. This technology was invented by IBM to allows for the dynamic real-time reprogramming of chips. In the abstract, computer logic is generally "etched" or "hard-wired" 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.[1]

Mechanism of action

eFuses can be made out of silicon or metal traces. In both cases, they work (blow) by electromigration, the phenomenon that electric flow causes the conductor material to move. Although electromigration is generally undesired in chip design as it causes failures, eFuses are made of weak traces that are designed to fail before others do.[2][3]

Uses

eFuses are initially marketed by IBM as a way 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.[2][4][5]

eFuses are perhaps more commonly used as a one-time programmable ROM. This ranges from writing unique information onto CPUs,[3] or in the case of game consoles and other restricted hardware, preventing downgrades by permanently recording a newer version. Both the Xbox 360 and the Nintendo Switch are known for using efuses this way.[6]

Implementations

eFuses used for performance adjustment or unique IDs:

eFuses known to be used for hardware restriction:

Variants

Resettable efuses are used for protecting circuits. They act similarly to resettable fuses, and are generally shipped as a standalone chip package.[11]

There are several ways of implementing an antifuse in silicon. See Antifuse ยง Antifuses in integrated circuits.

See also

References
  1. DCC (1989-03-14). "Method and apparatus for causing an open circuit in a conductive line". Archived from the original on 2017-02-11.
  2. Smith, Tony. "IBM eFuse to yield self-repairing, self-regulating CPUs". The Register.
  3. "Examining metal eFuses". EETAsia.
  4. "IBM introduces chip morphing technology". IBM. 2004-07-30. Archived from the original on 2010-07-24. Retrieved 2009-09-17.
  5. Port, Otis (2005-06-06). "Mighty Morphing Power Processors". BusinessWeek.
  6. "How the Nintendo Switch prevents downgrades by irreparably blowing its own fuses". Hacker Noon.
  7. Rizzolo, R. F.; Foote, T. G.; et al. (2007-02-13). "IBM System z9 eFUSE applications and methodology". doi:10.1147/rd.511.0065. Retrieved 2007-02-28.
  8. "Understanding the Xbox 360's Fusesets". Free60 Wiki archive.
  9. Speedy22 (2006-03-07). "XBOX 360 CPU Datasheet. Version 1.5" (PDF). Archived from the original (PDF) on 2006-03-15. Retrieved 2007-02-28.
  10. "IBM delivers Power-based chip for Microsoft Xbox 360 worldwide launch". IBM. 2005-10-25. Archived from the original on 2007-03-11. Retrieved 2007-02-28.
  11. "E-fuses". STMicroelectronics.
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