Precision 3630 - MEBx Hotkey (CTRL+P) not work

MEBx Hotkey is an option and it can be disabled in BIOS.

Ctrl-P only works when the post screen is displaying "Intel® MEBX: "  if you don't see that prompt, your bios is either lacking the configuration, or it is not enabled. if you don't have options related to the AMT/ME, look for an updated bios, and contact the manufacturer.  NEWER Versions use CTRL I or CTRL M or another key.

This option is not available in CHINA or RUSSIA etc.

1. Turn the system off and remove the power cord.
2. Open the chassis cover and locate the manageability mode sticker.
3. Verify the number on the manageability mode sticker.
4. Close the chassis cover, plug the power cord back into the system, and turn the system on.
5. At the Type the number corresponding with your selection: prompt, press the key for the number obtained from the sticker
6. (Figure 1).
   
    

    

   
   

Depends on bios. Secure boot must be OFF to set this

On the inside of the removable side cover there is a 2" x 1" label denoting the manageability mode with which the system was purchased .The system board is shipped in manufacturing mode and the end user or service provider must select the manageability option upon first boot. There are four manageability options that might be seen on the customer order according to the original configuration purchased.
For information on what manageability options were configured when the system was originally shipped

Selection can only be made 1 time