You
might be able to just rework an MMC3 as:
Disconnect MMC3 PPU A10,A11,A12 IN, tie all three to ground. Disconnect MMC3 CIRAM A10 OUT from CIRAM A10 IN, tie CIRAM A10 IN to PPU A10 (vertical mirroring / horizontal layout). Disconnect MMC3 CHR A10, A11, A12 OUT; connect CHR RAM A10, A11, A12 directly to PPU A10, A11, A12. Connect MMC3 A11 OUT to PRG ROM A19.
(Reference:
http://wiki.nesdev.com/w/index.php/MMC3_pinout )
But I don't know.
ALTERNATIVELY, the choice of mapper 245 looks strongly like this
(is yet another thing that) really just wants oversize UNROM with PRG RAM. Try this patch.
This patch WILL NOT work in FCEUX, because of a
hilariously awful "bug" fix they committed a while ago.
Attachment:
DoaE-RoLB-3.0-uxrom.ips [151 Bytes]
Downloaded 119 times
edit: apparently it only works in Nestopia. Maybe fishy...
I couldn't find any space to add a bus-conflict prevention table, so I've instead marked the header with submapper 1 for "do not enforce bus conflicts". If you play through a bit in an emulator, and find that it's no buggier than without my mapper hack, to make the hardware reproduction you will need to add an inverter (74'04, 74'00, 74'02, whatever) to the board to convert R/W from the NES into /OE for the PRG ROM.
An easy way to do is to use two 74'02s instead of two 74'32s, and reverse the 16 KiB slices in the image that you burn onto the 'PROM; this will leave you with two spare NOR gates, one of which can be used to prevent bus conflicts as above.
(I did set it up to write the requested bank to a byte which is "$FF" in the PRG ROM, so normal AND bus conflict behavior "should" produce the right value... still).Hashes to verify correctness:
Code:
$ md5sum *.nes
beae707ebc6db1a28192ceed44351054 Destiny of an Emperor; Rise of Lu Bu 3.0.nes
98eb6a1a81f3c216ee953554e51dc2b0 DoaE-RoLB-3.0-uxrom.nes
$ crc32 *.nes
76ca1eea Destiny of an Emperor; Rise of Lu Bu 3.0.nes
1bc29eb5 DoaE-RoLB-3.0-uxrom.nes
$ sha1sum *.nes
ae88e8d76f837a3af3e9cb28eaff005edc9fae80 Destiny of an Emperor; Rise of Lu Bu 3.0.nes
55d82e93b1a57eede0df400063f5d24f1d367132 DoaE-RoLB-3.0-uxrom.nes