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study/sabre/os/files/ProtectedMode/DPMI1.0Spec/ch4.4.html

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+When a DPMI client switches into protected mode, a unique interrupt
+descriptor table (IDT) is created for the client by the DPMI host.
+Initially, all software interrupts (except for Int 31H, Int 2FH and
+Int 21H Function 4CH) or external hardware interrupts are directed to
+a handler that simply reflects the interrupt to real mode; i.e. the
+DPMI host's default handler simply switches the CPU into real mode and
+re-issues the interrupt, so that it can be serviced by the original
+real mod owner of the interrupt.  The contents of the general
+registers and flags are passed to the real mode handler and the
+modified registers and flags are returned to the protected mode
+handler.  Segment registers and the stack pointer are not passed
+between modes; the contents of the segment registers after the switch
+to real mode are undefined, and the DPMI host automatically supplies a
+valid real mode stack. <p>
+
+DPMI clients can install their own distinct real mode or protected
+mode handlers for software and external hardware interrupts with <a
+href="api/310201.html">Functions 0201H</a> and <a
+href="api/310205.html">0205H</a> respectively.  If a protected mode
+handler is installed, it is called instead of any real mode handler or
+the DPMI host's default handler.  Just as in real mode, the protected
+mode handler can either service the interrupt and terminate with an
+IRET, or transfer to the next handler in the chain by executing a
+<tt>PUSHF/CALL</tt> or a <tt>FAR JMP</tt>.  The final handler in the
+protected mode handler chain (the DPMI host's default handler) will
+reflect the interrupt to real mode. <p>
+
+<hr>
+<img src="/icons/menu.sm.gif"><a href="ch4.4.1.html">Virtual Interrupts</a><br>
+<img src="/icons/menu.sm.gif"><a href="ch4.4.2.html">Hardware Interrupts</a><br>
+<img src="/icons/menu.sm.gif"><a href="ch4.4.3.html">Software Interrupts</a><br>
+
+