Effects of VGA "Address wrap" and "MAP13"&"MAP14" bits (CRTC Mode control register)?

[superfury]

Anyone knows what effects they're supposed to have on calculated addresses in linear VRAM
(In my system it's address before the is (
(VRAMStart(The start address high&low register)
+VRAMOffset(Offset calculated or provided by CPU with read/write operation)
)*4
)+plane)? During CPU access (the area between 0xA0000-0xBFFFF) and hardware rendering (to the output device)?

I've already read the VGA info at http://www.osdever.net/FreeVGA/vga/crtcreg.htm#17