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Warm/Cold Reset

Posted on 2004-08-26
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Last Modified: 2006-11-17
Depending upon the type of reset (Warm/Cold), the OS writes perticular code at a fixed address. I am not getting information about that address. I need to know (once PC is up), was it a warm reset or a cold reset?  How to siove this issue? Note that i am working on DOS os.

Dhaval

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Question by:dhavalshah
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For-Soft earned 25 total points
ID: 11903021
You can try to check status of two BIOS variables 40h:15h and 40h:16h.
POST uses those variables. In case of cold boot post will change those variables. If you put some value in them POST should change them.

In theory those variables are unused after POST, but some BIOSes can use them in another way.
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by:dimitry
dimitry earned 25 total points
ID: 11904057
Bios Area: 40h:0072h  Size: 2bytes
  1234H means Ctrl+Alt+Del reboot is in progress.  BIOS checks  this to avoid doing a "cold boot" with the time-consuming POST
  4321H means reset, preserving memory, 5678H, 9abcH, and abcdH (are internal PC Convertible codes)

However, as For-Soft mentioned, different BIOSes can behave realy different....
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by:For-Soft
ID: 11904617
The 40h:72h variable is to set what action BIOS should take when CTRL+ALT+DEL is used. It will not contain an information about how PC was boot.
With this variable we can tell BIOS what to do if CTRL+ALT+DEL is pressed.
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by:gtkfreak
ID: 11915921
INT 19h can be used to warm boot the system.
U can create dummy.com using debug.exe / debug.com and key in the bytes CD and 19
Then save your file
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