Some newer Macs remember how many hours and minutes they were turned on at all. This information is present on any Mac that has an xPRAM (extended parameter RAM). It contains a 16-bit value which tells, when being multiplicated with 5, how minutes the Macs was turned on since it was started up first. This value gets lost if
1. Your battery which keeps the information fails
2. You reset the PRAM by pressing Command-Option-R-P while booting
3. You press the red reset button which is present on some mainboards (it discharges the PRAM when pressed)
If any of this conditions take place, the Macs realizes this when starting up because the checksum (i think there is one), does'nt match the one it gets when recalculating one. If so, it resets the PRAM (and xPRAM, of course) to the default values. This means that the total-power-on information also gets lost and set to 0. You can use PRAM Time Manipulator if you're so fascinated by this value and want to know how many hours your Mac ran when you first need to repair it or something else. But i need to tell you that, because the value has only 2 bytes and the value is stored in 1/12ths of an hour (5 minute cycles), there are only 5461 h and 15 minutes possible. After that, the counter is reset to 0 and all will start over.
How to use it:
Start PRAM Time Manipulator. A movable modal dialog box will appear with two fields and two buttons. In the first field, you will see the current number of hours since the last change to the xPRAM. The second field shows the current number of minutes. BTW: don't wonder why this is always a multiple of 5! I said already that the value is saved in 5 minute cycles. If you enter a value which is not a multiple of 5, it would be rounded down (always!) to the next possible value. Edit the fields to any value you wish. You can also enter more than 60 minutes, it'll be automatically converted to hours and minutes. If you're sure you're doing the right thing, click Set and the program quickly talks to the clock chip and tells it the new power on time. If not, click Cancel and the program leaves the xPRAM untouched.
Does my Mac have an xPRAM?
Older Macs (SE, LC i think, some models of the II-series) don't have an xPRAM. You can find out about this when, if you start up PRAM Time Manipulator, hours and minutes are set to 0 even if you did'nt had affected the xPRAM in any way (clearing it or manipulating it in the past 5 minutes your Mac was on). You can change the value without bombs or so, but after a restart, your Mac forgets it. I don't know how to identify if there's an xPRAM installed, if someone knows, please tell me.
Some possible uses for PRAM Time Manipulator:
- reset the power-on-time after a discharge or clear of the xPRAM (write it down before zapping!)
- just viewing the power-on-time (works if you click Cancel).
- when selling a Mac, setting the time to a lower one because some people come with TechTool™, which can read this information, and when they see a high value, they did'nt take it even if you've put in a brand new hard disk
Remember: i'm not liable for any damages or something bad this program can do. If it damages your clock chip, let your PRAM battery give some of it's acid to the mainboard or something neat, that's your problem. Normally, nothing harmful should happen because the program uses the (unfortunately undocumented) routines of the operating system to write or read from and to the PRAM. I did'nt wrote this stuff. Or did i????? I don't reserve any rights on PRAM Time Manipulator, neither is there a copyright on it. Do with it what you want.
Improvements (with sample code) are always welcome:
manuelk@bluewin.ch OR mkasper@kagi.com
(I let you choose, both of them work, but kagi.com just forwards mail to bluewin.ch, but if i ever change my provider, the address at kagi.com knews about the new address)
