The Debug Registers
Starting with the 386, all IA32 processors provide hardware breakpoint detection. This is implemented using the processor's debug registers. These registers are illustrated in Figure 16-1 on page 377. Other processor functions associated with debug include:
The debug exception (Exception 1). This exception is generated when the processor encounters a breakpoint match on a condition specified in the debug registers.
The breakpoint instruction exception (Exception 3). This exception is generated when the processor executes the breakpoint (INT3) instruction.
The Trap bit in a task's TSS. Causes a debug exception when a task switch occurs to a task with this bit (the T bit) set to one.
The EFlags[RF]. When set to one by the debugger, ...