computing Computing is any goal-oriented activity requiring, benefiting from, or creating computer, computing machinery. It includes the study and experimentation of algorithmic processes, and the development of both computer hardware, hardware and softw ...

, an eFuse (electronic fuse) is a microscopic fuse put into a computer chip. This technology was invented by

IBM International Business Machines Corporation (using the trademark IBM), nicknamed Big Blue, is an American Multinational corporation, multinational technology company headquartered in Armonk, New York, and present in over 175 countries. It is ...

in 2004 to allow 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.

Mechanism of action

eFuses can be made out of silicon or metal traces. In both cases, they work (blow) by

electromigration Electromigration is the transport of material caused by the gradual movement of the ions in a Conductor (material), conductor due to the momentum transfer between conducting electrons and diffusing metal atoms. The effect is important in applicat ...

, the phenomenon where 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.

Uses

eFuses were 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. Today, most eFuses are used to etch

serialization In computing, serialization (or serialisation, also referred to as pickling in Python (programming language), Python) is the process of translating a data structure or object (computer science), object state into a format that can be stored (e. ...

or calibration data onto a chip thus making it a read-only value.

Descriptive term

eFuses are perhaps more commonly used as a one-time programmable ROM or write-restricted memory, and not actual physical electric fuses. This ranges from writing unique information onto CPUs, or in the case of game consoles and other restricted hardware, preventing downgrades by permanently recording a newer version. The

Xbox 360 The Xbox 360 is a home video game console developed by Microsoft. As the successor to the Xbox (console), original Xbox, it is the second console in the Xbox#Consoles, Xbox series. It was officially unveiled on MTV on May 12, 2005, with detail ...

Nintendo Switch The is a video game console developed by Nintendo and released worldwide in most regions on March 3, 2017. Released in the middle of the Eighth generation of video game consoles, eighth generation of home consoles, the Switch succeeded the ...

Pixel 6 The Pixel 6 and Pixel 6 Pro are a pair of Android (operating system), Android phablet smartphones designed, developed, and marketed by Google as part of the Google Pixel product line. They collectively serve as the successor to the Pixel 5. T ...

and Samsung Galaxy S22 are known for using eFuses this way.

Implementations

eFuses used for performance adjustment or unique IDs: * IBM

POWER5 The POWER5 is a microprocessor developed and fabricated by IBM. It is an improved version of the POWER4. The principal improvements are support for simultaneous multithreading (SMT) and an on-die memory controller. The POWER5 is a dual-core ...

and

POWER6 The POWER6 is a microprocessor developed by IBM that implemented the Power ISA#Power ISA v.2.05, Power ISA v.2.05. When it became available in systems in 2007, it succeeded the POWER5#POWER5+, POWER5+ as IBM's flagship Power microprocessor. It i ...

high-end

RISC In electronics and computer science, a reduced instruction set computer (RISC) is a computer architecture designed to simplify the individual instructions given to the computer to accomplish tasks. Compared to the instructions given to a comp ...

processors; probably all newer models *

IBM System z9 IBM System z9 is a line of IBM mainframe computers. The first models were available on September 16, 2005. The System z9 also marks the end of the previously used eServer zSeries naming convention. It was also the last mainframe computer ...

and

System z10 IBM System z10 is a line of IBM mainframes. The z10 Enterprise Class (EC) was announced on February 26, 2008. On October 21, 2008, IBM announced the z10 Business Class (BC), a scaled-down version of the z10 EC. The System z10 represents the ...

mainframe A mainframe computer, informally called a mainframe or big iron, is a computer used primarily by large organizations for critical applications like bulk data processing for tasks such as censuses, industry and consumer statistics, enterpris ...

processors * Sony/Toshiba/IBM Cell used in

PlayStation 3 The PlayStation 3 (PS3) is a home video game console developed and marketed by Sony Computer Entertainment (SCE). It is the successor to the PlayStation 2, and both are part of the PlayStation brand of consoles. The PS3 was first released on ...

. Not claimed to be used for downgrade prevention. * Intel Westmere CPUs; probably all newer models * TI MSP430 MCU family for Unique IDs. * TI FPD-Link SERDES for a variety of different settings. eFuses known to be used for hardware restriction: * IBM/Microsoft

Xenon Xenon is a chemical element; it has symbol Xe and atomic number 54. It is a dense, colorless, odorless noble gas found in Earth's atmosphere in trace amounts. Although generally unreactive, it can undergo a few chemical reactions such as the ...

CPU in the

game console. 768bits of fuses. * Samsung Knox devices use an eFuse to detect if a non-Samsung boot path has ever been run.

Variants

Resettable eFuses are used for protecting circuits. They act similarly to resettable fuses, and are generally shipped as a standalone chip package. There are several ways of implementing an antifuse in silicon: see .

References