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mappers/m4_MMC3.c: Fix memory mirroring #7

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Merged
rene merged 1 commit into from
May 25, 2026
Merged

mappers/m4_MMC3.c: Fix memory mirroring #7

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20 changes: 12 additions & 8 deletions src/mappers/m4_MMC3.c
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Original file line number Diff line number Diff line change
Expand Up @@ -121,7 +121,7 @@ struct _mmc3_mapper {
*/
static void m4_mapper_IRQ_count(mapper_t *m)
{
struct _mmc3_mapper *mmc3 = (struct _mmc3_mapper *)m;
struct _mmc3_mapper *mmc3 = (struct _mmc3_mapper *)m->data;

/* If the reload flag was set or the counter hit 0 */
if (mmc3->IRQ_counter == 0 || mmc3->IRQ_reload) {
Expand Down Expand Up @@ -201,7 +201,7 @@ static int m4_mapper_init(struct _mapper_t *m, cartridge_t *c)
mmc3->last_bank[1] = c->rom->prg_size - 0x4000;

/* Set PPU callback */
ppu_set_mapper_trigger_cb((mapper_t *)mmc3, m4_mapper_IRQ_count);
ppu_set_mapper_trigger_cb(m, m4_mapper_IRQ_count);
return 0;
}

Expand Down Expand Up @@ -294,10 +294,12 @@ uint8_t m4_prg_mem_handler(struct _mapper_t *m, enum mem_op op,
uint16_t address, uint8_t value)
{
uint64_t idx;
uint64_t prg_mask;
int reg;
cartridge_t *cartridge = m->cartridge;
struct _mmc3_mapper *mmc3 = (struct _mmc3_mapper *)m->data;

prg_mask = cartridge->rom->prg_size - 1;
switch (op) {
case CMEM_READ:
if (address >= 0x6000 && address <= 0x7fff) {
Expand All @@ -314,12 +316,12 @@ uint8_t m4_prg_mem_handler(struct _mapper_t *m, enum mem_op op,
((mmc3->reg_bank[6] & 0x3f) * 0x2000) + (address & 0x1fff);
else
idx = mmc3->last_bank[1] + (address & 0x1fff);
return cartridge->rom->prg_rom[idx];
return cartridge->rom->prg_rom[idx & prg_mask];

} else if (address >= 0xa000 && address <= 0xbfff) {
/* PRG mode: 0/1 - R:7 */
idx = ((mmc3->reg_bank[7] & 0x3f) * 0x2000) + (address & 0x1fff);
return cartridge->rom->prg_rom[idx];
return cartridge->rom->prg_rom[idx & prg_mask];

} else if (address >= 0xc000 && address <= 0xdfff) {
/* PRG mode: 0 - second last bank | 1 - R:6 */
Expand All @@ -328,12 +330,12 @@ uint8_t m4_prg_mem_handler(struct _mapper_t *m, enum mem_op op,
else
idx =
((mmc3->reg_bank[6] & 0x3f) * 0x2000) + (address & 0x1fff);
return cartridge->rom->prg_rom[idx];
return cartridge->rom->prg_rom[idx & prg_mask];

} else if (address >= 0xe000 && address <= 0xffff) {
/* PRG mode: 0/1 - fixed to the last bank */
idx = mmc3->last_bank[0] + (address & 0x1fff);
return cartridge->rom->prg_rom[idx];
return cartridge->rom->prg_rom[idx & prg_mask];
}
break;

Expand Down Expand Up @@ -407,6 +409,7 @@ uint8_t m4_chr_mem_handler(struct _mapper_t *m, enum mem_op op,
uint16_t address, uint8_t value)
{
uint64_t idx = 0;
uint64_t chr_mask;
cartridge_t *cartridge = m->cartridge;
struct _mmc3_mapper *mmc3 = (struct _mmc3_mapper *)m->data;

Expand Down Expand Up @@ -452,14 +455,15 @@ uint8_t m4_chr_mem_handler(struct _mapper_t *m, enum mem_op op,
}
}

chr_mask = cartridge->rom->chr_size - 1;
switch (op) {
case CMEM_READ:
return cartridge->rom->chr_rom[idx];
return cartridge->rom->chr_rom[idx & chr_mask];
break;

case CMEM_WRITE:
if (cartridge->chr_ram)
cartridge->rom->chr_rom[idx] = value;
cartridge->rom->chr_rom[idx & chr_mask] = value;
return value;
}

Expand Down
4 changes: 2 additions & 2 deletions src/ppu.c
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Original file line number Diff line number Diff line change
Expand Up @@ -666,7 +666,7 @@ void ppu_clock(void)

/* Populate sprite shift register with sprite data */
if (ppu.cycle == 261) {
for (i = 0; i < ppu.sprite_cnt; i++) {
for (i = 0; i < ppu.sprite_cnt && i < TOTAL_SPRITES_AUX; i++) {
/* First, let's find the corresponding row of the sprites
* to be plotted
*/
Expand Down Expand Up @@ -738,7 +738,7 @@ void ppu_clock(void)
idx_sp = 0;
sp_prio = 0;
cur_x = ppu.cycle - 1;
for (i = 0; i < ppu.sprite_cnt; i++) {
for (i = 0; i < ppu.sprite_cnt && i < TOTAL_SPRITES_AUX; i++) {
if (cur_x >= ppu.OAM_aux.sprites[i].X &&
cur_x < (ppu.OAM_aux.sprites[i].X + 8)) {
sp[0] = get_bit(ppu.sp_lsb[i], 0x80, 0);
Expand Down
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