diff --git a/src/mem.c b/src/mem.c
index 65eeaa3..1925fa0 100644
--- a/src/mem.c
+++ b/src/mem.c
@@ -2062,14 +2062,14 @@ void mem_add_bios()
         mem_mapping_add(&bios_mapping[6], 0xf8000, 0x04000, mem_read_bios,   mem_read_biosw,   mem_read_biosl,   mem_write_null, mem_write_nullw, mem_write_nulll, rom + (0x18000 & biosmask), MEM_MAPPING_EXTERNAL, 0);
         mem_mapping_add(&bios_mapping[7], 0xfc000, 0x04000, mem_read_bios,   mem_read_biosw,   mem_read_biosl,   mem_write_null, mem_write_nullw, mem_write_nulll, rom + (0x1c000 & biosmask), MEM_MAPPING_EXTERNAL, 0);
 
-        mem_mapping_add(&bios_high_mapping[0], 0xfffe0000, 0x04000, mem_read_bios,   mem_read_biosw,   mem_read_biosl,   mem_write_null, mem_write_nullw, mem_write_nulll, rom,                        0, 0);
-        mem_mapping_add(&bios_high_mapping[1], 0xfffe4000, 0x04000, mem_read_bios,   mem_read_biosw,   mem_read_biosl,   mem_write_null, mem_write_nullw, mem_write_nulll, rom + (0x4000  & biosmask), 0, 0);
-        mem_mapping_add(&bios_high_mapping[2], 0xfffe8000, 0x04000, mem_read_bios,   mem_read_biosw,   mem_read_biosl,   mem_write_null, mem_write_nullw, mem_write_nulll, rom + (0x8000  & biosmask), 0, 0);
-        mem_mapping_add(&bios_high_mapping[3], 0xfffec000, 0x04000, mem_read_bios,   mem_read_biosw,   mem_read_biosl,   mem_write_null, mem_write_nullw, mem_write_nulll, rom + (0xc000  & biosmask), 0, 0);
-        mem_mapping_add(&bios_high_mapping[4], 0xffff0000, 0x04000, mem_read_bios,   mem_read_biosw,   mem_read_biosl,   mem_write_null, mem_write_nullw, mem_write_nulll, rom + (0x10000 & biosmask), 0, 0);
-        mem_mapping_add(&bios_high_mapping[5], 0xffff4000, 0x04000, mem_read_bios,   mem_read_biosw,   mem_read_biosl,   mem_write_null, mem_write_nullw, mem_write_nulll, rom + (0x14000 & biosmask), 0, 0);
-        mem_mapping_add(&bios_high_mapping[6], 0xffff8000, 0x04000, mem_read_bios,   mem_read_biosw,   mem_read_biosl,   mem_write_null, mem_write_nullw, mem_write_nulll, rom + (0x18000 & biosmask), 0, 0);
-        mem_mapping_add(&bios_high_mapping[7], 0xffffc000, 0x04000, mem_read_bios,   mem_read_biosw,   mem_read_biosl,   mem_write_null, mem_write_nullw, mem_write_nulll, rom + (0x1c000 & biosmask), 0, 0);
+        mem_mapping_add(&bios_high_mapping[0], (AT && cpu_16bitbus) ? 0xfe0000 : 0xfffe0000, 0x04000, mem_read_bios,   mem_read_biosw,   mem_read_biosl,   mem_write_null, mem_write_nullw, mem_write_nulll, rom,                        0, 0);
+        mem_mapping_add(&bios_high_mapping[1], (AT && cpu_16bitbus) ? 0xfe4000 : 0xfffe4000, 0x04000, mem_read_bios,   mem_read_biosw,   mem_read_biosl,   mem_write_null, mem_write_nullw, mem_write_nulll, rom + (0x4000  & biosmask), 0, 0);
+        mem_mapping_add(&bios_high_mapping[2], (AT && cpu_16bitbus) ? 0xfe8000 : 0xfffe8000, 0x04000, mem_read_bios,   mem_read_biosw,   mem_read_biosl,   mem_write_null, mem_write_nullw, mem_write_nulll, rom + (0x8000  & biosmask), 0, 0);
+        mem_mapping_add(&bios_high_mapping[3], (AT && cpu_16bitbus) ? 0xfec000 : 0xfffec000, 0x04000, mem_read_bios,   mem_read_biosw,   mem_read_biosl,   mem_write_null, mem_write_nullw, mem_write_nulll, rom + (0xc000  & biosmask), 0, 0);
+        mem_mapping_add(&bios_high_mapping[4], (AT && cpu_16bitbus) ? 0xff0000 : 0xffff0000, 0x04000, mem_read_bios,   mem_read_biosw,   mem_read_biosl,   mem_write_null, mem_write_nullw, mem_write_nulll, rom + (0x10000 & biosmask), 0, 0);
+        mem_mapping_add(&bios_high_mapping[5], (AT && cpu_16bitbus) ? 0xff4000 : 0xffff4000, 0x04000, mem_read_bios,   mem_read_biosw,   mem_read_biosl,   mem_write_null, mem_write_nullw, mem_write_nulll, rom + (0x14000 & biosmask), 0, 0);
+        mem_mapping_add(&bios_high_mapping[6], (AT && cpu_16bitbus) ? 0xff8000 : 0xffff8000, 0x04000, mem_read_bios,   mem_read_biosw,   mem_read_biosl,   mem_write_null, mem_write_nullw, mem_write_nulll, rom + (0x18000 & biosmask), 0, 0);
+        mem_mapping_add(&bios_high_mapping[7], (AT && cpu_16bitbus) ? 0xffc000 : 0xffffc000, 0x04000, mem_read_bios,   mem_read_biosw,   mem_read_biosl,   mem_write_null, mem_write_nullw, mem_write_nulll, rom + (0x1c000 & biosmask), 0, 0);
 }
 
 int mem_a20_key = 0, mem_a20_alt = 0;
@@ -2104,7 +2104,7 @@ void mem_init()
         for (c = 0; c < (mem_size / 64); c++)
         {
                 isram[c] = 1;
-                if (c >= 0xa && c <= 0xf) 
+                if ((c >= 0xa && c <= 0xf) || (cpu_16bitbus && c >= 0xfe && c <= 0xff))
                         isram[c] = 0;
         }
 
@@ -2128,8 +2128,16 @@ void mem_init()
         mem_mapping_add(&ram_low_mapping, 0x00000, (mem_size > 640) ? 0xa0000 : mem_size * 1024, mem_read_ram,    mem_read_ramw,    mem_read_raml,    mem_write_ram, mem_write_ramw, mem_write_raml,   ram,  MEM_MAPPING_INTERNAL, NULL);
         if (mem_size > 1024)
         {
-                mem_set_mem_state(0x100000, (mem_size - 1024) * 1024, MEM_READ_INTERNAL | MEM_WRITE_INTERNAL);
-                mem_mapping_add(&ram_high_mapping, 0x100000, ((mem_size - 1024) * 1024), mem_read_ram,    mem_read_ramw,    mem_read_raml,    mem_write_ram, mem_write_ramw, mem_write_raml,   ram + 0x100000, MEM_MAPPING_INTERNAL, NULL);
+                if (cpu_16bitbus && mem_size > 16256)
+                {
+                        mem_set_mem_state(0x100000, (16256 - 1024) * 1024, MEM_READ_INTERNAL | MEM_WRITE_INTERNAL);
+                        mem_mapping_add(&ram_high_mapping, 0x100000, ((16256 - 1024) * 1024), mem_read_ram,    mem_read_ramw,    mem_read_raml,    mem_write_ram, mem_write_ramw, mem_write_raml,   ram + 0x100000, MEM_MAPPING_INTERNAL, NULL);
+                }
+                else
+                {
+                        mem_set_mem_state(0x100000, (mem_size - 1024) * 1024, MEM_READ_INTERNAL | MEM_WRITE_INTERNAL);
+                        mem_mapping_add(&ram_high_mapping, 0x100000, ((mem_size - 1024) * 1024), mem_read_ram,    mem_read_ramw,    mem_read_raml,    mem_write_ram, mem_write_ramw, mem_write_raml,   ram + 0x100000, MEM_MAPPING_INTERNAL, NULL);
+                }
         }
 	if (mem_size > 768)
         	mem_mapping_add(&ram_mid_mapping,   0xc0000, 0x40000, mem_read_ram,    mem_read_ramw,    mem_read_raml,    mem_write_ram, mem_write_ramw, mem_write_raml,   ram + 0xc0000,  MEM_MAPPING_INTERNAL, NULL);
@@ -2199,7 +2207,7 @@ void mem_resize()
         for (c = 0; c < (mem_size / 64); c++)
         {
                 isram[c] = 1;
-                if (c >= 0xa && c <= 0xf) 
+                if ((c >= 0xa && c <= 0xf) || (cpu_16bitbus && c >= 0xfe && c <= 0xff))
                         isram[c] = 0;
         }
 
@@ -2221,8 +2229,16 @@ void mem_resize()
         mem_mapping_add(&ram_low_mapping, 0x00000, (mem_size > 640) ? 0xa0000 : mem_size * 1024, mem_read_ram,    mem_read_ramw,    mem_read_raml,    mem_write_ram, mem_write_ramw, mem_write_raml,   ram,  MEM_MAPPING_INTERNAL, NULL);
         if (mem_size > 1024)
         {
-                mem_set_mem_state(0x100000, (mem_size - 1024) * 1024, MEM_READ_INTERNAL | MEM_WRITE_INTERNAL);
-                mem_mapping_add(&ram_high_mapping, 0x100000, (mem_size - 1024) * 1024, mem_read_ram,    mem_read_ramw,    mem_read_raml,    mem_write_ram, mem_write_ramw, mem_write_raml,   ram + 0x100000, MEM_MAPPING_INTERNAL, NULL);
+                if (cpu_16bitbus && mem_size > 16256)
+                {
+                        mem_set_mem_state(0x100000, (16256 - 1024) * 1024, MEM_READ_INTERNAL | MEM_WRITE_INTERNAL);
+                        mem_mapping_add(&ram_high_mapping, 0x100000, ((16256 - 1024) * 1024), mem_read_ram,    mem_read_ramw,    mem_read_raml,    mem_write_ram, mem_write_ramw, mem_write_raml,   ram + 0x100000, MEM_MAPPING_INTERNAL, NULL);
+                }
+                else
+                {
+                        mem_set_mem_state(0x100000, (mem_size - 1024) * 1024, MEM_READ_INTERNAL | MEM_WRITE_INTERNAL);
+                        mem_mapping_add(&ram_high_mapping, 0x100000, ((mem_size - 1024) * 1024), mem_read_ram,    mem_read_ramw,    mem_read_raml,    mem_write_ram, mem_write_ramw, mem_write_raml,   ram + 0x100000, MEM_MAPPING_INTERNAL, NULL);
+                }
         }
 	if (mem_size > 768)
 	        mem_mapping_add(&ram_mid_mapping,   0xc0000, 0x40000, mem_read_ram,    mem_read_ramw,    mem_read_raml,    mem_write_ram, mem_write_ramw, mem_write_raml,   ram + 0xc0000,  MEM_MAPPING_INTERNAL, NULL);