amiga/agnus_copper.cpp: 0x5c is actual h blank minimum position

mamedev · Jan 14, 2025 · faeca8f · faeca8f
1 parent ed86f1d
commit faeca8f
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Showing 2 changed files with 11 additions and 4 deletions.
diff --git a/src/mame/amiga/agnus_copper.cpp b/src/mame/amiga/agnus_copper.cpp
@@ -324,8 +324,9 @@ int agnus_copper_device::execute_next(int xpos, int ypos, bool is_blitter_busy,
 				return xpos;
 			}
 			// delay write to the next available DMA slot if not in blanking area
-			// - bchvolly (title), suprfrog & abreed (bottom playfield rows)
-			const bool horizontal_blank = xpos < 0x47;
+			// - suprfrog & abreed (bottom playfield rows).
+			// - beast, biochall and cd32 bios wants this to be 0x5c
+			const bool horizontal_blank = xpos <= 0x5c;
 			const int move_offset = horizontal_blank ? 0 : std::max(num_planes - 4, 0);
 
 			m_pending_offset = word0;
@@ -358,7 +359,7 @@ int agnus_copper_device::execute_next(int xpos, int ypos, bool is_blitter_busy,
 		/* handle a wait */
 		if ((word1 & 1) == 0)
 		{
-			const bool horizontal_blank = xpos < 0x47;
+			const bool horizontal_blank = xpos <= 0x5c;
 			const int wait_offset = horizontal_blank ? 0 : std::max(num_planes - 4, 0) + 1;
 
 			LOGINST("  WAIT %04x & %04x (currently %04x, num planes %d +%d)\n",

diff --git a/src/mame/amiga/amiga_m.cpp b/src/mame/amiga/amiga_m.cpp
@@ -1241,6 +1241,11 @@ void amiga_state::aga_map(address_map &map)
 
 void amiga_state::custom_chip_reset()
 {
+    // TODO: not entirely correct
+    // - OCS Denise returns open bus
+    // - ECS Denise should return 0xff << 8 | ID
+    // - AGA Lisa bits 15-10 are jumper selectable (at least on A4000), returns 0xfc << 8 | ID
+    // cfr. https://eab.abime.net/showpost.php?p=627136&postcount=59
 	CUSTOM_REG(REG_DENISEID) = m_denise_id;
 	CUSTOM_REG(REG_VPOSR) = m_agnus_id << 8;
 	CUSTOM_REG(REG_DDFSTRT) = 0x18;
@@ -1367,7 +1372,8 @@ uint16_t amiga_state::custom_chip_r(offs_t offset)
 			temp = CUSTOM_REG(REG_CLXDAT);
 			if (!machine().side_effects_disabled())
 				CUSTOM_REG(REG_CLXDAT) = 0;
-			// - "Barney [& Freddy] Mouse" requires bit 15 high all the time
+			// Undocumented bit 15 always high
+			// - "Barney [& Freddy] Mouse" will always detect a player-enemy hit out of iframe cycles otherwise
 			return temp | (1 << 15);
 
 		case REG_DENISEID: