From 0ed5cf6b3879c0b7d6adfe769354e55fe04d1d1b Mon Sep 17 00:00:00 2001
From: Lior Halphon <LIJI32@gmail.com>
Date: Wed, 8 Apr 2020 19:07:29 +0300
Subject: [PATCH] Proper MBC30 support, more accurate MBC3 emulation. Fixes
 #244

---
 Core/debugger.c | 23 ++++++++++++++---------
 Core/gb.h       |  6 +++---
 Core/mbc.c      | 11 +++++++++++
 3 files changed, 28 insertions(+), 12 deletions(-)

diff --git a/Core/debugger.c b/Core/debugger.c
index 71f0861..8e7151b 100644
--- a/Core/debugger.c
+++ b/Core/debugger.c
@@ -1420,15 +1420,20 @@ static bool mbc(GB_gameboy_t *gb, char *arguments, char *modifiers, const debugg
     }
 
     if (cartridge->mbc_type) {
-        static const char * const mapper_names[] = {
-            [GB_MBC1] = "MBC1",
-            [GB_MBC2] = "MBC2",
-            [GB_MBC3] = "MBC3",
-            [GB_MBC5] = "MBC5",
-            [GB_HUC1] = "HUC1",
-            [GB_HUC3] = "HUC3",
-        };
-        GB_log(gb, "%s\n", mapper_names[cartridge->mbc_type]);
+        if (gb->is_mbc30) {
+            GB_log(gb, "MBC30\n");
+        }
+        else {
+            static const char *const mapper_names[] = {
+                [GB_MBC1] = "MBC1",
+                [GB_MBC2] = "MBC2",
+                [GB_MBC3] = "MBC3",
+                [GB_MBC5] = "MBC5",
+                [GB_HUC1] = "HUC1",
+                [GB_HUC3] = "HUC3",
+            };
+            GB_log(gb, "%s\n", mapper_names[cartridge->mbc_type]);
+        }
         GB_log(gb, "Current mapped ROM bank: %x\n", gb->mbc_rom_bank);
         if (cartridge->has_ram) {
             GB_log(gb, "Current mapped RAM bank: %x\n", gb->mbc_ram_bank);
diff --git a/Core/gb.h b/Core/gb.h
index b4ef658..0b188d6 100644
--- a/Core/gb.h
+++ b/Core/gb.h
@@ -403,9 +403,8 @@ struct GB_gameboy_internal_s {
             } mbc2;
 
             struct {
-                uint8_t rom_bank:7;
-                uint8_t padding:1;
-                uint8_t ram_bank:4;
+                uint8_t rom_bank:8;
+                uint8_t ram_bank:3;
             } mbc3;
 
             struct {
@@ -538,6 +537,7 @@ struct GB_gameboy_internal_s {
             GB_STANDARD_MBC1_WIRING,
             GB_MBC1M_WIRING,
         } mbc1_wiring;
+        bool is_mbc30;
 
         unsigned pending_cycles;
                
diff --git a/Core/mbc.c b/Core/mbc.c
index d3791a1..2a96219 100644
--- a/Core/mbc.c
+++ b/Core/mbc.c
@@ -86,6 +86,10 @@ void GB_update_mbc_mappings(GB_gameboy_t *gb)
         case GB_MBC3:
             gb->mbc_rom_bank = gb->mbc3.rom_bank;
             gb->mbc_ram_bank = gb->mbc3.ram_bank;
+            if (!gb->is_mbc30) {
+                gb->mbc_rom_bank &= 0x7F;
+                gb->mbc_ram_bank &= 0x3;
+            }
             if (gb->mbc_rom_bank == 0) {
                 gb->mbc_rom_bank = 1;
             }
@@ -147,6 +151,13 @@ void GB_configure_cart(GB_gameboy_t *gb)
         }
     }
     
+    /* Detect MBC30 */
+    if (gb->cartridge_type->mbc_type == GB_MBC3) {
+        if (gb->rom_size > 0x200000 || gb->mbc_ram_size > 0x8000) {
+            gb->is_mbc30 = true;
+        }
+    }
+    
     /* Set MBC5's bank to 1 correctly */
     if (gb->cartridge_type->mbc_type == GB_MBC5) {
         gb->mbc5.rom_bank_low = 1;