A20 line fix by Greatpsycho.

src/mem.c

@@ -2316,16 +2316,19 @@ static uint8_t port_92_read(uint16_t port, void *priv)
 
 static void port_92_write(uint16_t port, uint8_t val, void *priv)
 {
-	if (val & 1)
+	if ((mem_a20_alt ^ val) & 2)
+	{
+		mem_a20_alt = val & 2;
+		mem_a20_recalc();
+	}
+
+	if ((~port_92_reg & val) & 1)
 	{
 		softresetx86();
 		cpu_set_edx();
 	}
 
-	port_92_reg = val & ~-1;
+	port_92_reg = val;
-
-	mem_a20_alt = val & 2;
-	mem_a20_recalc();
 }
 
 void port_92_clear_reset()

src/model.c

@@ -415,6 +415,7 @@ void xt_laserxt_init(void)
 void at_init(void)
 {
 	AT = 1;
+        mem_a20_key = mem_a20_alt = 0;
         common_init();
 	if (lpt_enabled)
 	{

src/ps1.c

@@ -300,6 +300,7 @@ void ps1mb_m2121_init(void)
                                 0x3ffff,
                                 0,
                                 MEM_MAPPING_EXTERNAL);
+	ps1_92 = 0;
         ps1_190 = 0;
         
         lpt1_init(0x3bc);
@@ -315,6 +316,7 @@ void ps1mb_m2133_init(void)
         io_sethandler(0x0102, 0x0004, ps1_m2121_read, NULL, NULL, ps1_m2121_write, NULL, NULL, NULL);
         io_sethandler(0x0190, 0x0001, ps1_m2121_read, NULL, NULL, ps1_m2121_write, NULL, NULL, NULL);
  
+	ps1_92 = 0;
         ps1_190 = 0;
        
         lpt1_init(0x3bc);

src/ps2.c

@@ -131,6 +131,7 @@ void ps2board_init(void)
         io_sethandler(0x0322, 0x0001, ps2_read, NULL, NULL, ps2_write, NULL, NULL, NULL);
         io_sethandler(0x0324, 0x0001, ps2_read, NULL, NULL, ps2_write, NULL, NULL, NULL);
         
+	ps2_92 = 0;
         ps2_190 = 0;
 
         lpt1_init(0x3bc);

src/scat.c

@@ -494,6 +494,7 @@ void scat_init()
         scat_regs[SCAT_DRAM_CONFIGURATION] = cpu_waitstates == 1 ? 2 : 0x12;
         scat_regs[SCAT_EXTENDED_BOUNDARY] = 0;
         scat_regs[SCAT_EMS_CONTROL] = 0;
+	scat_port_92 = 0;
 
         mem_mapping_set_addr(&ram_low_mapping, 0, 0x40000);