                                       CR4

Control Register 4


Graphical Breakdown:

bits
      31                          7 6                       0    
      [   Reserved                 |MCE|0|PSE|DE|TDS|PVI|VME]
                                     |     |   |  |   |   |
                                     |     |   |  |   |   |
                                     |     |   |  |   |   |
                          Machine    *     |   |  |   |   |
                          Check Enable     |   |  |   |   |
                                           |   |  |   |   |
                                   Page    *   |  |   |   |
                                   Size        |  |   |   |
                                 Extensions    |  |   |   |
                                               |  |   |   |
                                    Debugging  *  |   |   |
                                    Extensions    |   |   |
                                                  |   |   |
                                            Time  *   |   |
                                            Stamp     |   |
                                            Disable   |   |
                                                      |   |
                                            Protected *   |
                                            Mode Virtual  |
                                            Interrupts    |
                                                          |
                                                  Virtual *
                                                   8086
                                                   Mode
                                                   Extensions
                                    
                                    
CR4 Was not implemented until the Pentium and later 486's.  
After RESET, CR4 = 0.
