NVRAM content address offsets [modified]
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Hi, I want to be able to set the wake-up (or resume) time on a PC by programatically changing the contents of the BIOS NVRAM. Does anyone know the detail of the mapping of the parameters within NVRAM (specifically the offset of the wakeup time hours, minutes, seconds location and also the checksum location) - I AM assuming that these are fixed as other applications seem to be able to "wake-up" PC's programmatically. I've been "Googling" for ages on this and haven't had any luck ! UPDATE: Have now found that the RTC registers are what I need and they're accessable via port x'70' and x'71' Hopefully, I'm on my way !!! -- modified at 18:01 Sunday 15th July, 2007 UPDATE 2: Looks as though "something" is overwritting the RTC alarm registers at power down as they revert to the BIOS setup screen values. Anyone know anything about this ? (P.S. Believe the RTC is in the SiS962 south-bridge chip) -- modified at 3:45 Monday 16th July, 2007
Doug
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Hi, I want to be able to set the wake-up (or resume) time on a PC by programatically changing the contents of the BIOS NVRAM. Does anyone know the detail of the mapping of the parameters within NVRAM (specifically the offset of the wakeup time hours, minutes, seconds location and also the checksum location) - I AM assuming that these are fixed as other applications seem to be able to "wake-up" PC's programmatically. I've been "Googling" for ages on this and haven't had any luck ! UPDATE: Have now found that the RTC registers are what I need and they're accessable via port x'70' and x'71' Hopefully, I'm on my way !!! -- modified at 18:01 Sunday 15th July, 2007 UPDATE 2: Looks as though "something" is overwritting the RTC alarm registers at power down as they revert to the BIOS setup screen values. Anyone know anything about this ? (P.S. Believe the RTC is in the SiS962 south-bridge chip) -- modified at 3:45 Monday 16th July, 2007
Doug
The "something" is the BIOS setting the desired values, because the standard application for the BIOS alarm is to wake up at the desired time. It is therefore important that the registers be written once again during powerdown.
Cheers, Sebastian -- "If it was two men, the non-driver would have challenged the driver to simply crash through the gates. The macho image thing, you know." - Marc Clifton
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The "something" is the BIOS setting the desired values, because the standard application for the BIOS alarm is to wake up at the desired time. It is therefore important that the registers be written once again during powerdown.
Cheers, Sebastian -- "If it was two men, the non-driver would have challenged the driver to simply crash through the gates. The macho image thing, you know." - Marc Clifton
Hi Sebastian, Thanks for your reply ! I understand that the BIOS alarm values must be set into the RTC. But I would have thought that this would only happen when the BIOS setup screen was changed by the user - not at EVERY power down ! Accepting that this is what happens, where are the BIOS values stored in the interim and copied from ? My only thought is that it must be copied from NVRAM. Are they at fixed locations or dependent on the BIOS writer, and to be "hacked" by people like me that want to "zap" the process !!
Doug
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Hi Sebastian, Thanks for your reply ! I understand that the BIOS alarm values must be set into the RTC. But I would have thought that this would only happen when the BIOS setup screen was changed by the user - not at EVERY power down ! Accepting that this is what happens, where are the BIOS values stored in the interim and copied from ? My only thought is that it must be copied from NVRAM. Are they at fixed locations or dependent on the BIOS writer, and to be "hacked" by people like me that want to "zap" the process !!
Doug
Does anyone have any comments on my last posting ? :confused:
Doug