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eFuse
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<h2 id="mechanism-of-action">Mechanism of action</h2> <p>eFuses can be made out of silicon or metal traces. In both cases, they work (blow) by <a href="/facts/Electromigration/0aEaCFf7">electromigration</a>, 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.<a class="footnote-ref" id="fnref:3" href="#fn:3"><sup>3</sup></a><a class="footnote-ref" id="fnref:4" href="#fn:4"><sup>4</sup></a> </p> <h2 id="uses">Uses</h2> <p>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.<a class="footnote-ref" id="fnref:5" href="#fn:5"><sup>5</sup></a><a class="footnote-ref" id="fnref:6" href="#fn:6"><sup>6</sup></a><a class="footnote-ref" id="fnref:7" href="#fn:7"><sup>7</sup></a> Today, most eFuses are used to etch <a href="/facts/Serialization/T00auFvv">serialization</a> or calibration data onto a chip thus making it a read-only value.<a class="footnote-ref" id="fnref:8" href="#fn:8"><sup>8</sup></a> </p> <h2 id="descriptive-term">Descriptive term</h2> <p>eFuses are perhaps more commonly used as a one-time <a href="/facts/Programmable_ROM/amoyxIFx">programmable ROM</a> or write-restricted memory, and not actual physical electric fuses. This ranges from writing unique information onto CPUs,<a class="footnote-ref" id="fnref:9" href="#fn:9"><sup>9</sup></a> or in the case of game consoles and other restricted hardware, preventing downgrades by permanently recording a newer version. The <a href="/facts/Xbox_360/dYlE3mL5">Xbox 360</a>, <a href="/facts/Nintendo_Switch/UPy7Bcyu">Nintendo Switch</a>, <a href="/facts/Pixel_6/mpTmHyAk">Pixel 6</a> and <a href="/facts/Samsung_Galaxy_S22/CxQQTmcj">Samsung Galaxy S22</a> are known for using eFuses this way.<a class="footnote-ref" id="fnref:10" href="#fn:10"><sup>10</sup></a> </p> <h2 id="implementations">Implementations</h2> <p>eFuses used for performance adjustment or unique IDs: </p> <ul><li>IBM <a href="/facts/POWER5/bvj1ELch">POWER5</a> and <a href="/facts/POWER6/GqfSuMVM">POWER6</a> high-end <a href="/facts/Reduced_instruction_set_computer/aQbGM62p">RISC</a> processors; probably all newer models<a class="footnote-ref" id="fnref:11" href="#fn:11"><sup>11</sup></a></li> <li><a href="/facts/IBM_System_z9/lYQWHarc">IBM System z9</a> and <a href="/facts/IBM_z10/wqrYKC7C">System z10</a> <a href="/facts/Mainframe_computer/nrBR6rWa">mainframe</a> processors<a class="footnote-ref" id="fnref:12" href="#fn:12"><sup>12</sup></a></li> <li>Sony/Toshiba/IBM <a href="/facts/Cell_(processor)/p2MIQjMc">Cell</a> used in <a href="/facts/PlayStation_3/obhuo97V">PlayStation 3</a>. Not claimed to be used for downgrade prevention.</li> <li>Intel <a href="/facts/Westmere_(microarchitecture)/yB4HcYdY">Westmere</a> CPUs; probably all newer models<a class="footnote-ref" id="fnref:13" href="#fn:13"><sup>13</sup></a></li> <li><a href="/facts/Texas_Instruments/88NUhuHF">TI</a> <a href="/facts/MSP430/ngwhqtNN">MSP430</a> <a href="/facts/Microcontroller/MKrnAhnm">MCU</a> family for Unique IDs.</li> <li><a href="/facts/Texas_Instruments/88NUhuHF">TI</a> <a href="/facts/FPD-Link/IUs0RIsG">FPD-Link</a> <a href="/facts/SerDes/tzVeKyyV">SERDES</a> for a variety of different settings.</li></ul> <p>eFuses known to be used for hardware restriction: </p> <ul><li>IBM/Microsoft <a href="/facts/Xenon_(processor)/W8u6cvA2">Xenon</a> CPU in the <a href="/facts/Xbox_360/dYlE3mL5">Xbox 360</a> game console. 768 bits of fuses.<a class="footnote-ref" id="fnref:14" href="#fn:14"><sup>14</sup></a><a class="footnote-ref" id="fnref:15" href="#fn:15"><sup>15</sup></a><a class="footnote-ref" id="fnref:16" href="#fn:16"><sup>16</sup></a></li> <li><a href="/facts/Samsung_Knox/0YNtcp0X">Samsung Knox</a> devices use an eFuse to detect if a non-Samsung boot path has ever been run. <a class="footnote-ref" id="fnref:17" href="#fn:17"><sup>17</sup></a></li></ul> <h2 id="variants">Variants</h2> <p>Resettable eFuses are used for protecting circuits. They act similarly to <a href="/facts/Resettable_fuse/hu91A37j">resettable fuses</a>, and are generally shipped as a standalone chip package.<a class="footnote-ref" id="fnref:18" href="#fn:18"><sup>18</sup></a> </p><p>There are several ways of implementing an <a href="/facts/Antifuse/GqG8wx8q">antifuse</a> in silicon: see <a href="/facts/Antifuse/GqG8wx8q">Antifuse § Antifuses in integrated circuits</a>. </p> <h2 id="see-also">See also</h2> <ul><li><a href="/facts/Antifuse/GqG8wx8q">Antifuse</a></li> <li><a href="/facts/Reconfigurable_computing/J4b2JsRB">Reconfigurable computing</a></li></ul> <h2 id="references">References</h2> <ol> <li id="fn:1"><p>"IBM's eFuse technology portends adaptable chips". <a href="https://www.eetimes.com/ibms-efuse-technology-portends-adaptable-chips-2/" target="_blank">https://www.eetimes.com/ibms-efuse-technology-portends-adaptable-chips-2/</a> <a href="#fnref:1" class="footnote-back-ref">↩</a></p></li> <li id="fn:2"><p>DCC (1989-03-14). "Method and apparatus for causing an open circuit in a conductive line". Archived from the original on 2017-02-11. <a href="https://web.archive.org/web/20170211141010/http://patft.uspto.gov/netacgi/nph-Parser?Sect1=PTO1" target="_blank">https://web.archive.org/web/20170211141010/http://patft.uspto.gov/netacgi/nph-Parser?Sect1=PTO1</a> <a href="#fnref:2" class="footnote-back-ref">↩</a></p></li> <li id="fn:3"><p>Smith, Tony. "IBM eFuse to yield self-repairing, self-regulating CPUs". The Register. <a href="https://www.theregister.com/2004/08/02/ibm_efuse/" target="_blank">https://www.theregister.com/2004/08/02/ibm_efuse/</a> <a href="#fnref:3" class="footnote-back-ref">↩</a></p></li> <li id="fn:4"><p>"Examining metal eFuses". EETAsia. Archived from the original on 2021-06-14. Retrieved 2020-12-30. <a href="https://web.archive.org/web/20210614125738/https://archive.eetasia.com/www.eetasia.com/ART_8800717286_499485_TA_9b84ce1d.HTM" target="_blank">https://web.archive.org/web/20210614125738/https://archive.eetasia.com/www.eetasia.com/ART_8800717286_499485_TA_9b84ce1d.HTM</a> <a href="#fnref:4" class="footnote-back-ref">↩</a></p></li> <li id="fn:5"><p>Smith, Tony. "IBM eFuse to yield self-repairing, self-regulating CPUs". The Register. <a href="https://www.theregister.com/2004/08/02/ibm_efuse/" target="_blank">https://www.theregister.com/2004/08/02/ibm_efuse/</a> <a href="#fnref:5" class="footnote-back-ref">↩</a></p></li> <li id="fn:6"><p>"IBM introduces chip morphing technology". IBM. 2004-07-30. Archived from the original on 2010-07-24. Retrieved 2009-09-17. <a href="https://web.archive.org/web/20100724095358/http://www-304.ibm.com/jct03001c/press/us/en/pressrelease/7246.wss" target="_blank">https://web.archive.org/web/20100724095358/http://www-304.ibm.com/jct03001c/press/us/en/pressrelease/7246.wss</a> <a href="#fnref:6" class="footnote-back-ref">↩</a></p></li> <li id="fn:7"><p>Port, Otis (2005-06-06). "Mighty Morphing Power Processors". BusinessWeek. Archived from the original on May 29, 2005. <a href="https://web.archive.org/web/20050529023836/http://www.businessweek.com/magazine/content/05_23/b3936081_mz018.htm" target="_blank">https://web.archive.org/web/20050529023836/http://www.businessweek.com/magazine/content/05_23/b3936081_mz018.htm</a> <a href="#fnref:7" class="footnote-back-ref">↩</a></p></li> <li id="fn:8"><p>"Espressif ESP-IDF esp_mac.h". Espressif. 2023-06-08. Retrieved 2023-11-07. <a href="https://github.com/espressif/esp-idf/blob/master/components/esp_hw_support/include/esp_mac.h" target="_blank">https://github.com/espressif/esp-idf/blob/master/components/esp_hw_support/include/esp_mac.h</a> <a href="#fnref:8" class="footnote-back-ref">↩</a></p></li> <li id="fn:9"><p>"Examining metal eFuses". EETAsia. Archived from the original on 2021-06-14. Retrieved 2020-12-30. <a href="https://web.archive.org/web/20210614125738/https://archive.eetasia.com/www.eetasia.com/ART_8800717286_499485_TA_9b84ce1d.HTM" target="_blank">https://web.archive.org/web/20210614125738/https://archive.eetasia.com/www.eetasia.com/ART_8800717286_499485_TA_9b84ce1d.HTM</a> <a href="#fnref:9" class="footnote-back-ref">↩</a></p></li> <li id="fn:10"><p>Amadeo, Ron (2022-08-31). "Google gives developers a way to sidestep Android 13's one-way update". Ars Technica. Retrieved 2022-09-04. <a href="https://arstechnica.com/gadgets/2022/08/google-gives-developers-a-way-to-sidestep-android-13s-one-way-update/" target="_blank">https://arstechnica.com/gadgets/2022/08/google-gives-developers-a-way-to-sidestep-android-13s-one-way-update/</a> <a href="#fnref:10" class="footnote-back-ref">↩</a></p></li> <li id="fn:11"><p>Smith, Tony. "IBM eFuse to yield self-repairing, self-regulating CPUs". The Register. <a href="https://www.theregister.com/2004/08/02/ibm_efuse/" target="_blank">https://www.theregister.com/2004/08/02/ibm_efuse/</a> <a href="#fnref:11" class="footnote-back-ref">↩</a></p></li> <li id="fn:12"><p>Rizzolo, R. F.; Foote, T. G.; et al. (2007-02-13). "IBM System z9 eFUSE applications and methodology". IBM Journal of Research and Development. 51: 65–75. doi:10.1147/rd.511.0065. Retrieved 2007-02-28. <a href="http://www.research.ibm.com/journal/rd/511/rizzolo.html" target="_blank">http://www.research.ibm.com/journal/rd/511/rizzolo.html</a> <a href="#fnref:12" class="footnote-back-ref">↩</a></p></li> <li id="fn:13"><p>"Examining metal eFuses". EETAsia. Archived from the original on 2021-06-14. Retrieved 2020-12-30. <a href="https://web.archive.org/web/20210614125738/https://archive.eetasia.com/www.eetasia.com/ART_8800717286_499485_TA_9b84ce1d.HTM" target="_blank">https://web.archive.org/web/20210614125738/https://archive.eetasia.com/www.eetasia.com/ART_8800717286_499485_TA_9b84ce1d.HTM</a> <a href="#fnref:13" class="footnote-back-ref">↩</a></p></li> <li id="fn:14"><p>"Understanding the Xbox 360's Fusesets". Free60 Wiki. <a href="https://free60.org/Hardware/Fusesets/" target="_blank">https://free60.org/Hardware/Fusesets/</a> <a href="#fnref:14" class="footnote-back-ref">↩</a></p></li> <li id="fn:15"><p>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.{{cite web}}: CS1 maint: numeric names: authors list (link) <a href="https://web.archive.org/web/20060315071537/http://dwl.xbox-scene.com/tutorial/XBOX360cpu15data.pdf" target="_blank">https://web.archive.org/web/20060315071537/http://dwl.xbox-scene.com/tutorial/XBOX360cpu15data.pdf</a> <a href="#fnref:15" class="footnote-back-ref">↩</a></p></li> <li id="fn:16"><p>"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. <a href="https://web.archive.org/web/20070311071013/http://www-03.ibm.com/chips/news/2005/1025_xbox.html" target="_blank">https://web.archive.org/web/20070311071013/http://www-03.ibm.com/chips/news/2005/1025_xbox.html</a> <a href="#fnref:16" class="footnote-back-ref">↩</a></p></li> <li id="fn:17"><p>"What is a Knox Warranty Bit and how is it triggered?". docs.samsungknox.com. Retrieved 2024-07-16. <a href="https://docs.samsungknox.com/admin/knox-platform-for-enterprise/faq/#what-is-a-knox-warranty-bit-and-how-is-it-triggered" target="_blank">https://docs.samsungknox.com/admin/knox-platform-for-enterprise/faq/#what-is-a-knox-warranty-bit-and-how-is-it-triggered</a> <a href="#fnref:17" class="footnote-back-ref">↩</a></p></li> <li id="fn:18"><p>"E-fuses". STMicroelectronics. <a href="https://www.st.com/en/power-management/e-fuses.html" target="_blank">https://www.st.com/en/power-management/e-fuses.html</a> <a href="#fnref:18" class="footnote-back-ref">↩</a></p></li> </ol>