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Vol. 2A 3-609
INSTRUCTION SET REFERENCE, A-M
MOV—Move to/from Debug Registers
Flags Affected
The OF, SF, ZF, AF, PF, and CF flags are undefined.
Protected Mode Exceptions
#GP(0) If the current privilege level is not 0.
#UD If CR4.DE[bit 3] = 1 (debug extensions) and a MOV instruction
is executed involving DR4 or DR5.
If the LOCK prefix is used.
#DB If any debug register is accessed while the DR7.GD[bit 13] = 1.
Real-Address Mode Exceptions
#UD If CR4.DE[bit 3] = 1 (debug extensions) and a MOV instruction
is executed involving DR4 or DR5.
If the LOCK prefix is used.
#DB If any debug register is accessed while the DR7.GD[bit 13] = 1.
Virtual-8086 Mode Exceptions
#GP(0) The debug registers cannot be loaded or read when in virtual-
8086 mode.
Compatibility Mode Exceptions
Same exceptions as in protected mode.
64-Bit Mode Exceptions
#GP(0) If the current privilege level is not 0.
#UD If CR4.DE[bit 3] = 1 (debug extensions) and a MOV instruction
is executed involving DR4 or DR5.
If the LOCK prefix is used.
#DB If any debug register is accessed while the DR7.GD[bit 13] = 1.