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INSTRUCTION SET REFERENCE
MOVMove to/from Debug Registers (Continued)
Real-Address Mode Exceptions
#UD
If the DE (debug extensions) bit of CR4 is set and a MOV instruction is
executed involving DR4 or DR5.
#DB
If any debug register is accessed while the GD flag in debug register DR7
is set.
Virtual-8086 Mode Exceptions
#GP(0)
The debug registers cannot be loaded or read when in virtual-8086 mode.
