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 |
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.