From 2d412c74d22b8839d51eef78af45c2ba31a3c800 Mon Sep 17 00:00:00 2001
From: 0kmg <9137159+0kmg@users.noreply.github.com>
Date: Wed, 11 Aug 2021 12:53:07 -0800
Subject: [PATCH] bus/nes: Fixed bugs in Game Star type "A" boards. (#8425)

- Corrects certain games not loading or loading with corrupt graphics in different multicarts.
---
 hash/nes.xml                      |  8 +++---
 src/devices/bus/nes/multigame.cpp | 45 ++++++++++++++-----------------
 src/devices/bus/nes/multigame.h   |  7 ++---
 3 files changed, 28 insertions(+), 32 deletions(-)

diff --git a/hash/nes.xml b/hash/nes.xml
index 6e175b88eb0..417330c226b 100644
--- a/hash/nes.xml
+++ b/hash/nes.xml
@@ -79799,7 +79799,7 @@ be better to redump them properly. -->
 		</part>
 	</software>
 
-	<software name="mc_6gs1" supported="partial">
+	<software name="mc_6gs1">
 		<description>6 in 1 (GK-L01A)</description>
 		<year>19??</year>
 		<publisher>Game Star</publisher>
@@ -79821,7 +79821,7 @@ be better to redump them properly. -->
 		</part>
 	</software>
 
-	<software name="mc_6gs2" supported="partial">
+	<software name="mc_6gs2">
 		<description>6 in 1 (SuperGK-L02A)</description>
 		<year>19??</year>
 		<publisher>Game Star?</publisher>
@@ -80013,13 +80013,13 @@ be better to redump them properly. -->
 		</part>
 	</software>
 
+<!-- This has at least seven 16K NROM games. Perhaps there's a menu in the last 16K bank or it's meant to be reset based? -->
 	<software name="mc_68" supported="no">
 		<description>68 in 1</description>
 		<year>19??</year>
 		<publisher>&lt;unknown&gt;</publisher>
 		<part name="cart" interface="nes_cart">
-			<feature name="slot" value="bmc_gka" />
-			<feature name="pcb" value="BMC-GKA" /> <!-- Mapper 57? -->
+			<feature name="slot" value="bmc_gka" /> <!-- FIXME: wrong board! -->
 			<dataarea name="chr" size="65536">
 				<rom name="68-in-1 (1-f1 race meq &amp; 68-maross dli).chr" size="65536" crc="26c744ee" sha1="01af2b2fe5ba33b2de26e6b4fea6f40eddeda3fc" offset="00000" status="baddump" />
 			</dataarea>
diff --git a/src/devices/bus/nes/multigame.cpp b/src/devices/bus/nes/multigame.cpp
index 38123976175..02bac0698bc 100644
--- a/src/devices/bus/nes/multigame.cpp
+++ b/src/devices/bus/nes/multigame.cpp
@@ -182,8 +182,8 @@ nes_bmc_gb63_device::nes_bmc_gb63_device(const machine_config &mconfig, const ch
 {
 }
 
-nes_bmc_gka_device::nes_bmc_gka_device(const machine_config &mconfig, const char *tag, device_t *owner, uint32_t clock)
-	: nes_nrom_device(mconfig, NES_BMC_GKA, tag, owner, clock), m_latch1(0), m_latch2(0)
+nes_bmc_gka_device::nes_bmc_gka_device(const machine_config &mconfig, const char *tag, device_t *owner, u32 clock)
+	: nes_nrom_device(mconfig, NES_BMC_GKA, tag, owner, clock)
 {
 }
 
@@ -661,19 +661,16 @@ void nes_bmc_gb63_device::pcb_reset()
 void nes_bmc_gka_device::device_start()
 {
 	common_start();
-	save_item(NAME(m_latch1));
-	save_item(NAME(m_latch2));
+	save_item(NAME(m_reg));
 }
 
 void nes_bmc_gka_device::pcb_reset()
 {
-	m_chr_source = m_vrom_chunks ? CHRROM : CHRRAM;
 	prg16_89ab(0);
 	prg16_cdef(0);
-	chr8(0, m_chr_source);
+	chr8(0, CHRROM);
 
-	m_latch1 = 0;
-	m_latch2 = 0;
+	m_reg[0] = m_reg[1] = 0;
 }
 
 void nes_bmc_gkb_device::device_start()
@@ -1772,33 +1769,31 @@ uint8_t nes_bmc_gb63_device::read_h(offs_t offset)
 
  iNES: mapper 57
 
- In MESS: Supported.
+ In MAME: Supported.
 
  -------------------------------------------------*/
 
-void nes_bmc_gka_device::write_h(offs_t offset, uint8_t data)
+u8 nes_bmc_gka_device::read_m(offs_t offset)
+{
+	LOG_MMC(("bmc_gka read_m, offset: %04x\n", offset));
+	return 0; // TODO: menus differ by jumper/DIP settings readable at 0x6000.
+}
+
+void nes_bmc_gka_device::write_h(offs_t offset, u8 data)
 {
 	LOG_MMC(("bmc_gka write_h, offset: %04x, data: %02x\n", offset, data));
 
-	if (offset & 0x0800)
-		m_latch2 = data;
-	else
-		m_latch1 = data;
+	m_reg[BIT(offset, 11)] = data;
 
-	if (m_latch2 & 0x80)
-		prg32(2 | (m_latch2 >> 6));
-	else
-	{
-		prg16_89ab((m_latch2 >> 5) & 0x03);
-		prg16_cdef((m_latch2 >> 5) & 0x03);
-	}
+	u8 bank = m_reg[1] >> 5;
+	u8 mode = BIT(m_reg[1], 4);
+	prg16_89ab(bank & ~mode);
+	prg16_cdef(bank | mode);
 
-	set_nt_mirroring((m_latch2 & 0x08) ? PPU_MIRROR_HORZ : PPU_MIRROR_VERT);
-
-	chr8((m_latch1 & 0x03) | (m_latch2 & 0x07) | ((m_latch2 & 0x10) >> 1), CHRROM);
+	chr8((m_reg[0] & 0x40) >> 3 | (m_reg[1] & 0x04) | (m_reg[BIT(m_reg[0], 7)] & 0x03), CHRROM);
+	set_nt_mirroring(BIT(m_reg[1], 3) ? PPU_MIRROR_HORZ : PPU_MIRROR_VERT);
 }
 
-
 /*-------------------------------------------------
 
  Board BMC-GKB
diff --git a/src/devices/bus/nes/multigame.h b/src/devices/bus/nes/multigame.h
index bb8f80642e4..b6d8fe3c5b6 100644
--- a/src/devices/bus/nes/multigame.h
+++ b/src/devices/bus/nes/multigame.h
@@ -396,9 +396,10 @@ class nes_bmc_gka_device : public nes_nrom_device
 {
 public:
 	// construction/destruction
-	nes_bmc_gka_device(const machine_config &mconfig, const char *tag, device_t *owner, uint32_t clock);
+	nes_bmc_gka_device(const machine_config &mconfig, const char *tag, device_t *owner, u32 clock);
 
-	virtual void write_h(offs_t offset, uint8_t data) override;
+	virtual u8 read_m(offs_t offset) override;
+	virtual void write_h(offs_t offset, u8 data) override;
 
 	virtual void pcb_reset() override;
 
@@ -407,7 +408,7 @@ protected:
 	virtual void device_start() override;
 
 private:
-	uint8_t m_latch1, m_latch2;
+	u8 m_reg[2];
 };