Increasing USB-NES Compatibility

When USB-NES can not automatically identify a game cart properly, you can apply the patch scripts shown in this section to the OVERRIDE.TXT file on the USB-NES drive to specifically read out your game.

The easiest way to install a new override into USB-NES is to open the OVERRIDE.TXT file and copy the complete mapper override script listed below into the file starting from the first line and then save. If the green light blinks on USB-NES after you saved the file it means USB-NES accepted the save (no light blink in manual override mode).

When the unit is started or DETECT.TXT is read without¹ a cartridge in the slot, USB-NES uses the default_map_index setting in SETTINGS.TXT to determine which override mapper to use by default. Index slot zero starts from wherever the first valid override header is detected from the beginning of the file and counts up from there. You may also enable the manual override mode to force the unit to use the override.

Documentation on the mapper override header hex values and the script sequences is available starting at the Mapper Header Descriptor Type.

In this default no-cart-detected startup mode, it is helpful to set REPORT.TXT_enable = 1 in SETTINGS.TXT so you can view the override information via REPORT.TXT without triggering an unwanted auto-detection via DETECT.TXT, after the game is eventually plugged into the slot.

Available Override Scripts

$ 1A53454E  08 00 21 00    00 00 00 00 00 00 00 00
8000  0000  0000  0000     0E 00 00 00       00 00
1111110000000cba=--------.PRG!
3D Worldrunner              @!

$ 1A53454E  08 00 21 00    00 00 00 00 00 00 00 00
8000  0000  0000  0000     0E 00 00 00       00 00
1100000000000cba=--------.PRG!
Castlevania                 @!

$ 1A53454E  02 02 31 00    00 00 00 00 00 00 00 00
8000  0000  0000  0000     0F 0D 00 00       00 00
111100000000001A=--------.PRG!
DK Classics                 @!

$ 1A53454E  08 00 21 00    00 00 00 00 00 00 00 00
8000  0000  0000  0000     0E 00 00 00       00 00
1111111111010cba=--------.PRG!
Double Dribble              @!

$ 1A53454E  04 02 12 00    00 00 70 00 00 00 00 00
8000  0000  6000  0000     0E 0D 0D 00       03 80
1110000000000000=0000dcba.PRG!
1010000000000000=000dcba0.PRG!
1000000000000000=00001100.PRG 
1110000000000000=00000000.PRG!
1110000000000000=00010000.PRG!
Dragon Warrior              @!

$ 1A53454E  02 04 31 00   00 00 00 00 00 00 00 00
8000  0000  0000  0000    0F 0D 00 00       00 00
10111000011001bA=--------.PRG!
Adventure Island            @!

$ 1A53454E  08 00 12 00   00 00 70 00 00 00 00 00
8000  0000  6000  0000    0E 00 0D 00       03 80
1110000000000000=0000dcba.PRG!
1000000000000000=00001100.PRG 
1110000000000000=00000000.PRG!
1110000000000000=00010000.PRG!
Legend of Zelda             @!

$ 1A53454E  08 00 21 00   00 00 00 00 00 00 00 00
8000  0000  0000  0000    0E 00 00 00       00 00
1111111001101cbA=--------.PRG!
Pro Wrestling               @!

$ 1A53454E  08 00 20 00   00 00 00 00 00 00 00 00
8000  0000  0000  0000    0E 00 00 00       00 00
1111111111010cba=--------.PRG!
Top Gun                     @!

$ 1A53454E  08 10 10 00   00 00 00 00 00 00 00 00
8000  0000  0000  0000    0E 0D 00 00       01 80
1110000000000000=0000dcba.PRG!
1010000000000000=000dcba0.PRG!
1000000000000000=00001100.PRG!
Willow                      @!

$ 1A53454E  08 00 20 00   00 00 00 00 00 00 00 00
8000  0000  0000  0000    0E 00 00 00       00 00
1100000011111cba=--------.PRG!
Zanac                       @!

$ 1A53454E  10 20 42 00   00 00 70 0C 00 00 00 00
8000  8000  6000  0000    0D 0D 0D 00       03 40  
1000000000000000=00100110.PRG 
1000000000000001=001edcba.PRG!
1000000000000000=00100110.PRG 
1000000000000001=000edcba.PRG!
0101000000000000=00000000.PRG 
0101000100000000=00000000.PRG 
1000000000000000=00100000.PRG 
1010000000000001=10110000.PRG!
1010000000000001=00000000.PRG!
Mother Repro fix            @!

Binary Mapper Overrides

These legacy binary override files (in the .zip archive) can be installed to USB-NES if the OVERRIDE.BIN_enable setting is set to 1 or the NES_2.0___enable setting is set to 2. Note that modifying OVERRIDE.BIN affects OVERRIDE.TXT and vice-versa because they essentially represent the same data.

OVERRIDE.BIN .zip (for NES/FC Title)	Details
3-D Battles of Worldrunner, The	UNROM 128 KB – banking table @ $FC00
Castlevania	UNROM 128 KB – banking table @ $C000
Donkey Kong Classics	CNROM 32 KB + 16 KB – banking table @ $F003
Double Dribble	UNROM 128 KB – banking table @ $FFD0
Dragon Warrior¹	SAROM 64 KB + 16 KB – 8 KB save abstract
Hudson’s Adventure Island	CNROM 32 KB + 32 KB – banking table @ $B865
Legend of Zelda, The¹	SNROM 128 KB – 8 KB save abstract
Pro Wrestling	UNROM 128 KB – banking table @ $FE69
Top Gun	UNROM 128 KB – banking table @ $FFD0
Willow	SLROM 128 KB + 128 KB
Zanac	UNROM 128 KB – banking table @ $C0F8

Current library of off-the-shelf override.bin files for several NES/FC titles, and the details of the mapper override

^{1. This override will create a .NES image that sets a byte in location 10 describing the size of cart NVRAM to be 8KB. This is part of the NES 2.0 spec and can be safely nullified if an emulator does not like it.}