Mapper hacking and debugging.

Discuss technical or other issues relating to programming the Nintendo Entertainment System, Famicom, or compatible systems.

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DrWho198
Posts: 25
Joined: Mon Feb 23, 2015 8:05 pm

Re: Mapper hacking and debugging.

Post by DrWho198 » Tue Feb 24, 2015 4:32 pm

lidnariq wrote:This is really straightforward hardware to add. It's a 74'138 and a latch such as a (74'74 or 74'161) on top of a board already containing an MMC3.

Wire the 74'138 to detect writes to $41xx by connecting:
R/W to /G1a
A13 to /G1b
M2 to G2
/ROMSEL to A
A8 to B
A14 to C
Then
74'138 /Y7 to latch CLK
CPU D2 to latch data in
latch data out to CHR A18.
wow, thanks... I didn't expect this. I'll still have to check if the rom depends on the other mappers. But this information might make a repro possible again.

pakosup
Posts: 16
Joined: Mon Apr 24, 2017 10:23 pm

Re: Mapper hacking and debugging.

Post by pakosup » Tue Aug 06, 2019 2:49 am

lidnariq wrote:This is really straightforward hardware to add. It's a 74'138 and a latch such as a (74'74 or 74'161) on top of a board already containing an MMC3.
Seems it's not so simple. Trying to make repro of AV Mei Shao Nv Zhan Shi (Unl)
20190612_215858.jpg
If mmc3 completely ignore writing to $41xx then this game should work on mapper 04 (just with broken graphics).
Probably 116 mapper do something with mmc3 registers on writing to $41xx because game behaves wrong (on character selection screen and during fight I have freeze and garbled graphics).

For easier reproduction we can change code and move control register for CHR to $6000, because no WRAM in this game and we can use signals from mmc3 instead of 74'138 (like in mapper 189).
If only we can make the rest code work on mapper 4.

lidnariq
Posts: 8918
Joined: Sun Apr 13, 2008 11:12 am
Location: Seattle

Re: Mapper hacking and debugging.

Post by lidnariq » Tue Aug 06, 2019 1:28 pm

If it crashes like that, odds are good that it's using MMC1 mode in order to change what would be MMC3's fixed bank, and so I fear an MMC3 mapper hack would be impossible.

pakosup
Posts: 16
Joined: Mon Apr 24, 2017 10:23 pm

Re: Mapper hacking and debugging.

Post by pakosup » Tue Dec 17, 2019 1:01 am

I've managed to remove protection from this rom, now it doesn't change mapper modes to vrc and mmc1. But circuit suggested earlier in this topic doesn't work properly (probably due to bus conflicts). So I 'm going to implement my idea to utilize wram /ce
Attachments
AV Mei Shao Nv Zhan Shi (Unl)[deprotected].ips
Removes copy protection from original game. Now can be run on MMC3
(105 Bytes) Downloaded 20 times

User avatar
nintendo2600
Posts: 318
Joined: Mon Mar 30, 2009 4:40 pm

Re: Mapper hacking and debugging.

Post by nintendo2600 » Tue Jan 14, 2020 8:41 pm

pakosup wrote:
Tue Dec 17, 2019 1:01 am
I've managed to remove protection from this rom, now it doesn't change mapper modes to vrc and mmc1. But circuit suggested earlier in this topic doesn't work properly (probably due to bus conflicts). So I 'm going to implement my idea to utilize wram /ce
Any chance you have mapper hacks to something more conventional like MMC1 or MMC3 for Lethal Weapon (enforcers) or Cobra Mission pirate famicom games? They both use crazy stuff (mapper 90 or 118 I think?) I wanna play them on my real nintendo and not just on an emulator. Zapper and a CRT for lightgun games or GTFO right? :)

pakosup
Posts: 16
Joined: Mon Apr 24, 2017 10:23 pm

Re: Mapper hacking and debugging.

Post by pakosup » Fri Jan 17, 2020 8:47 am

I thought about mmc5 because it supports 512KB of chr.
But I've done this game on mmc3 with additional logic.
20200103_195518~01.jpg
By the way Cobra Mission can be easily converted to mmc3, I can give you the patch.

aquasnake
Posts: 74
Joined: Fri Sep 13, 2019 11:22 pm

Re: Mapper hacking and debugging.

Post by aquasnake » Sun Jan 19, 2020 1:45 am

Mapper 115 is more suitable

just ignore the writes to $6000 and fetch $6001.bit[0] as mapped A18

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