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Type multi Mapper 935 Original mapper 0+4 PCB marks BS007 BS-007 Tags: Uploaded: 2021-08-10 12:01:04

One of those few cartridgs with MMC3 and NROM games.
MMC3 alone cannot run NROM games because it has fixed bank at $c000/$e000 so extra logic is needed to fool it's CPU-A14 line to 0 (and extra register at $6000-$7fff to extend PRG to 1MB)

 fedcba9876543210
[011.....ECCPPaxb] $6000-$7fff (writable only when $a001 = $80)
         |||||+-+-- PRG mode
         ||||| +--- PRG A14 (see bellow)
         ||||+----- PRG A18 (always)
         |||+------ PRG A19 (always)
         ||+------- CHR A17 (always)
         |+-------- CHR A18 (always) 
		 +--------- PRG enabled: 0=yes, 1=no (without that feature, menu is 1000000 in 1, not 2000000 in 1)
			
[.S......] - MMC3's PRG sel register ($8000
[...ppppp] - MMC3's PRG REG 0 (accessed via $8001 when $8000=6)
[...qqqqq] - MMC3's PRG REG 1 (accessed via $8001 when $8000=6)


Sba |  $8000  |  $a000  |  $c000  |  $e000  | note:
----+---------+---------+---------+---------+
00* | PPppppp | PPqqqqq | PP11110 | PP11111 | used for up to four different 128k MMC3 games
010 | PP0ppxp | PP0qqxq | PP0ppxp | PP0qqxq | used for 16k NROM
011 | PP1pp0p | PP1qq0q | PP1pp1p | PP1qq1q | used for 32k UNROM

10* | PP11110 | PPqqqqq | PPppppp | PP11111 | used for up to four different 128k MMC3 games
110 | PP011x0 | PP0qqxq | PP011x0 | PP0qqxq | nonsense
111 | PP11101 | PP1qq0q | PP11110 | PP1qq1q | nonsense


//dumping script - M2 toggling must be ON
			cpuWrite(0xa001, 0x80);
			cpuWrite(0x8000, 6);
			for (int i = 0; i < 1024 / 8; ++i) {
				cpuWrite(0x6000 | shi(i, 6, 4) | shi(i, 5, 3), 0);
				cpuWrite(0x8001, (byte)(i & 0x1f));
				cpuRead(0x8000, 0x9fff);
			}

			cpuWrite(0x8000, 2);
			for (int i = 0; i < 512 / 1; ++i) {
				cpuWrite(0x6000 | shi(i, 8, 6) | shi(i, 7, 5), 0);
				cpuWrite(0x8001, i & 0x7f);
				ppuRead(0x1000, 0x13ff);
			}
				
				
----------------

The cartridge has two quirks:
* First one is that Mario, when started, can't be controlled, you need to press start again (this behaves same on real hardware and emu)
* Second, the first game (Captain Tsubasa 2 in Arabic) hangs after start (there is music but black background). This happens on real cart, but when dumped and played on emu - it works correctly! 
This game is infamous for writing to CHR registers values > $7F (while it has 128kB CHR RAM). 
The ROM, floating around internet, called "Captain Tsubasa Vol. II - Super Striker (Arabic) (Unl) [!].nes" has all those writes (tens of it) corrected by replacing 
  STA $8001 
with
  JSR $FFC0
and adding this little stub:
 0F:FFC0: 29 7F     AND #$7F
 0F:FFC2: 8D 01 80  STA $8001 
 0F:FFC5: 60        RTS
(the game on this 2000000 in 1 cartridge does not have this correction).
It should not matter because MMC CHR A17 is not routed to anything.

The second difference is that

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