Gets reset few times a week

[Yoshihide]

Does anyone have a clue to why the "Hours of Use" (the one you get in TechTool) gets reset a few times a week?

It should display something like 43000 hours since 2004/3/19, but about once or twice a week, TechTool would display 30 hours since 2004/3/19.

Since the manufacture date (2004/3/19) doesn't get reset, and only the hours of use, I'm guessing it's not the PRAM battery.

Has anyone experienced similar problems?

 

[Yoshihide]

Seems like the PRAM Hours of Use parameter won't record anything above 43690 Hours. After that, it returns back to 0.

Is there a limit to how much hours the PRAM can record? 43690 Hours seems quite an odd number to me.

 

[~Coxy]

43690 hours = 2621440 minutes.

That makes me guess that somewhere in the PRAM is 18 bits for the total uptime count, which gets incremented every 10 minutes.

 

[Nico]

And then after reaching that number, the counter overflows and goes back to zero automatically. It's the same problem the Unix timestamp will face in 2038 on 32-bit computers.