document new fmsx_mapper_type_mode values, and others, in the readme

README.md

@@ -4,3 +4,46 @@ fmsx
 this is a port of fMSX 4.9 to the libretro API
 
 source : http://fms.komkon.org/fMSX/
+
+
+## Recognized file extension
+* .rom .mx1 .mx2 .ROM .MX1 .MX2 - for ROM images
+* .dsk .DSK - for 360/720kB disk images
+* .cas .CAS - for fMSX tape files
+
+
+## Configuration options
+
+Specify these in your RetroArch core options:
+
+    fmsx_mode=MSX2+*|MSX1|MSX2
+    fmsx_video_mode=NTSC*|PAL
+    fmsx_mapper_type_mode=Guess Mapper Type A*|Guess Mapper Type B|Generic 8kB|Generic 16kB|Konami5 8kB|Konami4 8kB|ASCII 8kB|ASCII 16kB|GameMaster2|FMPAC
+    fmsx_ram_pages=Auto*|64KB|128KB|256KB|512KB
+    fmsx_vram_pages=Auto*|32KB|64KB|128KB|192KB
+
+A star (*) indicates this is the default setting.
+
+
+## BIOS
+These BIOS ROMs are required for execution:
+* MSX1: MSX.ROM
+* MSX2: MSX2.ROM, MSX2EXT.ROM
+* MSX2+: MSX2P.ROM, MSX2PEXT.ROM
+
+Optional; loaded when found:
+* DISK.ROM
+* FMPAC.ROM
+* KANJI.ROM
+* MSXDOS2.ROM (MSX2/2+)
+* PAINTER.ROM (MSX2/2+)
+* RS232.ROM
+* CMOS.ROM
+* GMASTER2.ROM, GMASTER.ROM
+
+
+## Technical details
+
+Video: 16bpp RGB565 272x228 (544x228 in 512px MSX2 screen modes).
+
+Audio: rendered in 48kHz 16b mono.