# Identifying small battery-like component of Power Mac G5

**URL:** <https://boards.straightdope.com/t/identifying-small-battery-like-component-of-power-mac-g5/542673>\
**Category:** Factual Questions\
**Created:** [June 10, 2010, 4:47pm UTC](https://boards.straightdope.com/t/identifying-small-battery-like-component-of-power-mac-g5/542673 "2010-06-10T16:47:39Z")\
**Posts on this page:** 5\
**Page:** 1

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**Author:** ![Animastryfe](https://avatars.discourse-cdn.com/v4/letter/a/8797f3/32.png) [@Animastryfe](https://boards.straightdope.com/u/Animastryfe)\
**Post date:** [June 10, 2010, 4:47pm UTC](https://boards.straightdope.com/t/identifying-small-battery-like-component-of-power-mac-g5/542673/1 "2010-06-10T16:47:39Z")

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Please help me figure out what this component in a Power Mac G5 is. In the [picture](http://www.ifixit.com/Guide/Repair/Installing-Power-Mac-G5-Graphics-Card/1955/2) for the fifth step, there seems to be a white, battery like component above the top left corner of the yellow box. What is it?

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**Author:** ![JoeH2O](https://avatars.discourse-cdn.com/v4/letter/j/9de053/32.png) [@JoeH2O](https://boards.straightdope.com/u/JoeH2O)\
**Post date:** [June 10, 2010, 4:51pm UTC](https://boards.straightdope.com/t/identifying-small-battery-like-component-of-power-mac-g5/542673/2 "2010-06-10T16:51:45Z")

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It looks like it is the logic board’s backup battery that powers the clock and internal settings of the PMU in the absence of power from the mains.

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**Author:** ![Animastryfe](https://avatars.discourse-cdn.com/v4/letter/a/8797f3/32.png) [@Animastryfe](https://boards.straightdope.com/u/Animastryfe)\
**Post date:** [June 10, 2010, 4:58pm UTC](https://boards.straightdope.com/t/identifying-small-battery-like-component-of-power-mac-g5/542673/3 "2010-06-10T16:58:18Z")

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Thank you.

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**Author:** ![DCnDC](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/dcndc/32/2842_2.png) [@DCnDC](https://boards.straightdope.com/u/DCnDC)\
**Post date:** [June 10, 2010, 5:01pm UTC](https://boards.straightdope.com/t/identifying-small-battery-like-component-of-power-mac-g5/542673/4 "2010-06-10T17:01:12Z")

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Just out of curiosity why do you ask?

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**Author:** ![gotpasswords](https://avatars.discourse-cdn.com/v4/letter/g/c57346/32.png) [@gotpasswords](https://boards.straightdope.com/u/gotpasswords)\
**Post date:** [June 11, 2010, 12:28pm UTC](https://boards.straightdope.com/t/identifying-small-battery-like-component-of-power-mac-g5/542673/5 "2010-06-11T12:28:18Z")

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This is the PRAM backup [battery](http://www.ifixit.com/Guide/Repair/Installing-Power-Mac-G5-Backup-Battery/1951/1) - or in IBM-type terms, the BIOS battery.