> An interrupt (INT) is actually a real-mode call...OS/2 is protected mode, 

An interrupt is no such thing. The difference between real and protected 
mode, as far as interrupts are concerned is as follows:
       * The realmode IDT is stuck (usually) at 0:0 with a limit of 0x3ff
         The protectedmode IDT is stuck anywhere with a limit of up to 0x7ff
       * The realmode IDT uses 16:16 seg/offs pair entries
         The protectedmode IDT uses three different 64-bit entry types.
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