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Re:Building a replacement 386/486 CMOS battery by adrianmonk on Monday December 23, 2024 @01:17PM (#42496403)
Yeah, those are a thing on old Sun workstations. They have a clock and they also store a small amount of data.

https://www.sun3arc.org/FAQ/sun-nvram-hostid.faq.phtml

I remember replacing one in the mid 1990s. The machine's ethernet address is stored on this chip, and I believe it's battery-backed RAM (not flash, EEPROM, etc.), so when the battery dies, the data on the chip is lost.

When you install a new chip, you need to program in the ethernet address so the machine can get on the network. The proper thing to do is use the factory-assigned ethernet address to ensure that it is unique. But you can't get the address from the old chip. So, like many people, I just picked some random numbers. It worked.

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