The External Registers (sometimes called the General Registers) each have their own unique I/O location in the VGA, although sometimes the Read Port differs from the Write port, and some are Read-only.. See the Accessing the VGA Registers section for more detals.  
Miscellaneous Output Register (Read at 3CCh, Write at 3C2h)
7 6 5 4 3 2 1 0
VSYNCP HSYNCP O/E Page Clock Select RAM En. I/OAS
   
Feature Control Register (Read at 3CAh, Write at 3BAh (mono) or 3DAh (color))
7 6 5 4 3 2 1 0
FC1 FC0
   
Input Status #0 Register (Read-only at 3C2h)
7 6 5 4 3 2 1 0
SS
   
Input Status #1 Register (Read at 3BAh (mono) or 3DAh (color))
7 6 5 4 3 2 1 0
VRetrace DD
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