genesis: only save the actual saveram (instead of an overly large file) in some cases with MD cart. disable automatic saveram (that didn't exist anyway) in most non-saveram carts. for mega CD, reduce size of EBRAM cart to 16KiB. it's still enough for a total of 3 Shining Force CD saves, so no complaining.

genplus-gx/cinterface/cinterface.c

@@ -12,6 +12,7 @@
 #include "genesis.h"
 #include "md_ntsc.h"
 #include "sms_ntsc.h"
+#include "eeprom_i2c.h"
 
 char GG_ROM[256] = "GG_ROM"; // game genie rom
 char AR_ROM[256] = "AR_ROM"; // actin replay rom
@@ -196,6 +197,33 @@ GPGX_EX void gpgx_advance(void)
 	nsamples = audio_update(soundbuffer);
 }
 
+// internal: computes sram size (no brams)
+int saveramsize(void)
+{
+	if (!sram.on)
+		return 0;
+	switch (sram.custom)
+	{
+	case 0: // plain bus access saveram
+		break;
+	case 1: // i2c
+		return eeprom_i2c.config.size_mask + 1;
+	case 2: // spi
+		return 0x10000; // it doesn't appear to mask anything internally
+	case 3: // 93c
+		return 0x10000; // SMS only and i don't have time to look into it
+	default:
+		return 0x10000; // who knows
+	}
+	// figure size for plain bus access saverams
+	{
+		int startaddr = sram.start / 8192;
+		int endaddr = sram.end / 8192 + 1;
+		int size = (endaddr - startaddr) * 8192;
+		return size;
+	}
+}
+
 GPGX_EX void gpgx_clear_sram(void)
 {
 	// clear sram
@@ -329,7 +357,7 @@ GPGX_EX const char* gpgx_get_memdom(int which, void **area, int *size)
 		if (sram.on)
 		{
 			*area = sram.sram;
-			*size = 0x10000;
+			*size = saveramsize();
 			return "SRAM";
 		}
 		else return NULL;
@@ -356,7 +384,7 @@ GPGX_EX void gpgx_get_sram(void **area, int *size)
 	if (sram.on)
 	{
 		*area = sram.sram;
-		*size = 0x10000;
+		*size = saveramsize();
 	}
 	else if (scd.cartridge.id)
 	{

genplus-gx/core/cart_hw/eeprom_i2c.c

@@ -37,6 +37,7 @@
  ****************************************************************************************/
 
 #include "shared.h"
+#include "eeprom_i2c.h"
 
 #define GAME_CNT 28
 
@@ -56,45 +57,6 @@
  * which uses D1-read=SDA, D0-write=SDA, D1-write=SCL. Accolade also has a custom-chip mapper which may even use a third method. 
  */
 
-typedef struct
-{
-  uint8 address_bits;     /* number of bits needed to address memory: 7, 8 or 16 */
-  uint16 size_mask;       /* depends on the max size of the memory (in bytes) */
-  uint16 pagewrite_mask;  /* depends on the maximal number of bytes that can be written in a single write cycle */
-  uint32 sda_in_adr;      /* 68000 memory address mapped to SDA_IN */
-  uint32 sda_out_adr;     /* 68000 memory address mapped to SDA_OUT */
-  uint32 scl_adr;         /* 68000 memory address mapped to SCL */
-  uint8 sda_in_bit;       /* bit offset for SDA_IN */
-  uint8 sda_out_bit;      /* bit offset for SDA_OUT */
-  uint8 scl_bit;          /* bit offset for SCL */
-} T_CONFIG_I2C;
-
-typedef enum
-{
-  STAND_BY = 0,
-  WAIT_STOP,
-  GET_SLAVE_ADR,
-  GET_WORD_ADR_7BITS,
-  GET_WORD_ADR_HIGH,
-  GET_WORD_ADR_LOW,
-  WRITE_DATA,
-  READ_DATA
-} T_STATE_I2C;
-
-typedef struct
-{
-  uint8 sda;            /* current /SDA line state */
-  uint8 scl;            /* current /SCL line state */
-  uint8 old_sda;        /* previous /SDA line state */
-  uint8 old_scl;        /* previous /SCL line state */
-  uint8 cycles;         /* current operation cycle number (0-9) */
-  uint8 rw;             /* operation type (1:READ, 0:WRITE) */
-  uint16 slave_mask;    /* device address (shifted by the memory address width)*/
-  uint16 word_address;  /* memory address */
-  T_STATE_I2C state;    /* current operation state */
-  T_CONFIG_I2C config;  /* EEPROM characteristics for this game */
-} T_EEPROM_I2C;
-
 typedef struct
 {
   char game_id[16];

genplus-gx/core/cart_hw/eeprom_i2c.h

@@ -39,6 +39,47 @@
 #ifndef _EEPROM_I2C_H_
 #define _EEPROM_I2C_H_
 
+typedef struct
+{
+  uint8 address_bits;     /* number of bits needed to address memory: 7, 8 or 16 */
+  uint16 size_mask;       /* depends on the max size of the memory (in bytes) */
+  uint16 pagewrite_mask;  /* depends on the maximal number of bytes that can be written in a single write cycle */
+  uint32 sda_in_adr;      /* 68000 memory address mapped to SDA_IN */
+  uint32 sda_out_adr;     /* 68000 memory address mapped to SDA_OUT */
+  uint32 scl_adr;         /* 68000 memory address mapped to SCL */
+  uint8 sda_in_bit;       /* bit offset for SDA_IN */
+  uint8 sda_out_bit;      /* bit offset for SDA_OUT */
+  uint8 scl_bit;          /* bit offset for SCL */
+} T_CONFIG_I2C;
+
+typedef enum
+{
+  STAND_BY = 0,
+  WAIT_STOP,
+  GET_SLAVE_ADR,
+  GET_WORD_ADR_7BITS,
+  GET_WORD_ADR_HIGH,
+  GET_WORD_ADR_LOW,
+  WRITE_DATA,
+  READ_DATA
+} T_STATE_I2C;
+
+typedef struct
+{
+  uint8 sda;            /* current /SDA line state */
+  uint8 scl;            /* current /SCL line state */
+  uint8 old_sda;        /* previous /SDA line state */
+  uint8 old_scl;        /* previous /SCL line state */
+  uint8 cycles;         /* current operation cycle number (0-9) */
+  uint8 rw;             /* operation type (1:READ, 0:WRITE) */
+  uint16 slave_mask;    /* device address (shifted by the memory address width)*/
+  uint16 word_address;  /* memory address */
+  T_STATE_I2C state;    /* current operation state */
+  T_CONFIG_I2C config;  /* EEPROM characteristics for this game */
+} T_EEPROM_I2C;
+
+extern T_EEPROM_I2C eeprom_i2c;
+
 /* Function prototypes */
 extern void eeprom_i2c_init();
 

genplus-gx/core/cart_hw/sram.c

@@ -186,14 +186,16 @@ void sram_init()
       sram.on = 0;
     }
 
-    /* by default, enable backup RAM for ROM smaller than 2MB */
+    // by default, enable backup RAM for ROM smaller than 2MB
+	/*
     else if (cart.romsize <= 0x200000)
     {
-      /* 64KB static RAM mapped to $200000-$20ffff */
+      // 64KB static RAM mapped to $200000-$20ffff
       sram.start = 0x200000;
       sram.end = 0x20ffff;
       sram.on = 1;
     }
+	*/
   }
 }
 

genplus-gx/core/cd_hw/cd_cart.c

@@ -191,8 +191,9 @@ void cd_cart_init(void)
   {
     /* enable 512K backup RAM cartridge when booting from CD (Mode 2) */
     //scd.cartridge.id = 6;
-	scd.cartridge.id = 4; // use 128K instead, which is the size of a real ebram cart
+	//scd.cartridge.id = 4; // use 128K instead, which is the size of a real ebram cart
 						// bizhawk doesn't need the extra space because it gives each game its own anyway
+	  scd.cartridge.id = 1; // 16K to be size-frugal
   }
 
   /* RAM cartridge enabled ? */