diff --git a/src/video/vid_oak_oti.c b/src/video/vid_oak_oti.c
index a32ed8201..f6e70a0de 100644
--- a/src/video/vid_oak_oti.c
+++ b/src/video/vid_oak_oti.c
@@ -8,7 +8,7 @@
  *
  *		Oak OTI037C/67/077 emulation.
  *
- * Version:	@(#)vid_oak_oti.c	1.0.14	2018/10/02
+ * Version:	@(#)vid_oak_oti.c	1.0.15	2018/10/07
  *
  * Authors:	Sarah Walker, <http://pcem-emulator.co.uk/>
  *		Miran Grca, <mgrca8@gmail.com>
@@ -29,11 +29,18 @@
 #include "vid_oak_oti.h"
 #include "vid_svga.h"
 
-#define BIOS_37C_PATH			L"roms/video/oti/bios.bin"
-#define BIOS_67_AMA932J_PATH	L"roms/machines/ama932j/oti067.bin"
-#define BIOS_77_PATH			L"roms/video/oti/oti077.vbi"
+#define BIOS_037C_PATH			L"roms/video/oti/bios.bin"
+#define BIOS_067_AMA932J_PATH		L"roms/machines/ama932j/oti067.bin"
+#define BIOS_077_PATH			L"roms/video/oti/oti077.vbi"
 
 
+enum {
+    OTI_037C,
+    OTI_067 = 2,
+    OTI_067_AMA932J,
+    OTI_077 = 5
+};
+
 typedef struct {
     svga_t svga;
 
@@ -42,14 +49,13 @@ typedef struct {
     int index;
     uint8_t regs[32];
 
+    uint8_t chip_id;
     uint8_t pos;
-
-	uint8_t enable_register;
+    uint8_t enable_register;
+    uint8_t dipswitch_val;
 	
     uint32_t vram_size;
     uint32_t vram_mask;
-
-    uint8_t chip_id;
 } oti_t;
 
 static video_timings_t timing_oti   = {VIDEO_ISA, 6, 8,16, 6, 8,16};
@@ -61,34 +67,43 @@ oti_out(uint16_t addr, uint8_t val, void *p)
     oti_t *oti = (oti_t *)p;
     svga_t *svga = &oti->svga;
     uint8_t old;
-	uint8_t idx;
+    uint8_t idx, enable;
+
+    if (!oti->chip_id && !(oti->enable_register & 1) && (addr != 0x3C3))
+	return;
 
-	if (!(oti->enable_register & 1) && addr != 0x3C3)
-			return;	
-	
     if ((((addr&0xFFF0) == 0x3D0 || (addr&0xFFF0) == 0x3B0) && addr < 0x3de) &&
 	!(svga->miscout & 1)) addr ^= 0x60;
 
     switch (addr) {
 	case 0x3C3:
-		oti->enable_register = val & 1;
-		return;
-		
+		if (!oti->chip_id) {
+			oti->enable_register = val & 1;
+			return;
+		} else
+			break;
+
 	case 0x3D4:
-		svga->crtcreg = val;
+		if (oti->chip_id)
+			svga->crtcreg = val & 0x3f;
+		else
+			svga->crtcreg = val;	/* FIXME: The BIOS wants to set the test bit? */
 		return;
 
 	case 0x3D5:
-		if (svga->crtcreg & 0x20)
+		if (oti->chip_id && (svga->crtcreg & 0x20))
 			return;
-		if (((svga->crtcreg & 31) < 7) && (svga->crtc[0x11] & 0x80))
+		idx = svga->crtcreg;
+		if (!oti->chip_id)
+			idx &= 0x1f;
+		if ((idx < 7) && (svga->crtc[0x11] & 0x80))
 			return;
-		if (((svga->crtcreg & 31) == 7) && (svga->crtc[0x11] & 0x80))
+		if ((idx == 7) && (svga->crtc[0x11] & 0x80))
 			val = (svga->crtc[7] & ~0x10) | (val & 0x10);
-		old = svga->crtc[svga->crtcreg & 31];
-		svga->crtc[svga->crtcreg & 31] = val;
+		old = svga->crtc[idx];
+		svga->crtc[idx] = val;
 		if (old != val) {
-			if ((svga->crtcreg & 31) < 0xE || (svga->crtcreg & 31) > 0x10) {
+			if ((idx < 0x0e) || (idx > 0x10)) {
 				svga->fullchange = changeframecount;
 				svga_recalctimings(svga);
 			}
@@ -96,30 +111,60 @@ oti_out(uint16_t addr, uint8_t val, void *p)
 		break;
 
 	case 0x3DE: 
-		oti->index = val; 
+		if (oti->chip_id)
+			oti->index = val & 0x1f;
+		else
+			oti->index = val;
 		return;
 
 	case 0x3DF:
-		idx = oti->index & 0x1f;
+		idx = oti->index;
+		if (!oti->chip_id)
+			idx &= 0x1f;
 		oti->regs[idx] = val;
 		switch (idx) {
 			case 0xD:
-				if (oti->chip_id)
-				{
+				if (oti->chip_id == OTI_067) {
 					svga->vram_display_mask = (val & 0xc) ? oti->vram_mask : 0x3ffff;
+					if (!(val & 0x80))
+						svga->vram_display_mask = 0x3ffff;
+
 					if ((val & 0x80) && oti->vram_size == 256)
 						mem_mapping_disable(&svga->mapping);
 					else
 						mem_mapping_enable(&svga->mapping);
-					if (!(val & 0x80))
-						svga->vram_display_mask = 0x3ffff;
-				}
-				else
-				{
-					if (val & 0x80)
-							mem_mapping_disable(&svga->mapping);
+				} else if (oti->chip_id == OTI_077) {
+					svga->vram_display_mask = (val & 0xc) ? oti->vram_mask : 0x3ffff;
+
+					switch ((val & 0xc0) >> 6) {
+						case 0x00:	/* 256 kB of memory */
+						default:
+							enable = (oti->vram_size >= 256);
+							if (val & 0xc)
+								svga->vram_display_mask = MIN(oti->vram_mask, 0x3ffff);
+							break;
+						case 0x01:	/* 1 MB of memory */
+						case 0x03:
+							enable = (oti->vram_size >= 1024);
+							if (val & 0xc)
+								svga->vram_display_mask = MIN(oti->vram_mask, 0x7ffff);
+							break;
+						case 0x20:	/* 512 kB of memory */
+							enable = (oti->vram_size >= 512);
+							if (val & 0xc)
+								svga->vram_display_mask = MIN(oti->vram_mask, 0xfffff);
+							break;
+					}
+
+					if (enable)
+						mem_mapping_enable(&svga->mapping);
 					else
-							mem_mapping_enable(&svga->mapping);
+						mem_mapping_disable(&svga->mapping);
+				} else {
+					if (val & 0x80)
+						mem_mapping_disable(&svga->mapping);
+					else
+						mem_mapping_enable(&svga->mapping);
 				}
 				break;
 
@@ -140,33 +185,57 @@ oti_in(uint16_t addr, void *p)
 {
     oti_t *oti = (oti_t *)p;
     svga_t *svga = &oti->svga;
-    uint8_t temp;
-	
-	if (!(oti->enable_register & 1) && addr != 0x3C3)
-			return 0xff;	
+    uint8_t idx, temp;
 	
+    if (!oti->chip_id && !(oti->enable_register & 1) && (addr != 0x3C3))
+	return 0xff;
+
     if ((((addr&0xFFF0) == 0x3D0 || (addr&0xFFF0) == 0x3B0) && addr < 0x3de) &&
 	!(svga->miscout & 1)) addr ^= 0x60;
 	
     switch (addr) {
-	case 0x3C3:
-		temp = oti->enable_register;
+	case 0x3C2:
+		if ((svga->vgapal[0].r + svga->vgapal[0].g + svga->vgapal[0].b) >= 0x50)
+			temp = 0;
+		else
+			temp = 0x10;
 		break;
-		
+
+	case 0x3C3:
+		if (oti->chip_id)
+			temp = svga_in(addr, svga);
+		else
+			temp = oti->enable_register;
+		break;
+
+                case 0x3CF:
+                return svga->gdcreg[svga->gdcaddr & 0xf];
+
 	case 0x3D4:
 		temp = svga->crtcreg;
 		break;
 
 	case 0x3D5:
-		if (svga->crtcreg & 0x20)
-			temp = 0xff;
-		else
-			temp = svga->crtc[svga->crtcreg & 31];
+		if (oti->chip_id) {
+			if (svga->crtcreg & 0x20)
+				temp = 0xff;
+			else
+				temp = svga->crtc[svga->crtcreg];
+		} else
+			temp = svga->crtc[svga->crtcreg & 0x1f];
 		break;
 
 	case 0x3DA:
+		if (oti->chip_id) {
+			temp = svga_in(addr, svga);
+			break;
+		}
+
                 svga->attrff = 0;
-                svga->attrff = 0;
+		/*The OTI-037C BIOS waits for bits 0 and 3 in 0x3da to go low, then reads 0x3da again
+		  and expects the diagnostic bits to equal the current border colour. As I understand
+		  it, the 0x3da active enable status does not include the border time, so this may be
+		  an area where OTI-037C is not entirely VGA compatible.*/
                 svga->cgastat &= ~0x30;
                 /* copy color diagnostic info from the overscan color register */
                 switch (svga->attrregs[0x12] & 0x30)
@@ -196,17 +265,23 @@ oti_in(uint16_t addr, void *p)
                                 svga->cgastat |= 0x20;
                         break;
                 }
-                return svga->cgastat;
+                temp = svga->cgastat;
+		break;
 
-	case 0x3DE: 
-		temp = oti->index | (oti->chip_id << 5);
+	case 0x3DE:
+		temp = oti->index;
+		if (oti->chip_id)
+			temp |= (oti->chip_id << 5);
 		break;	       
 
-	case 0x3DF: 
-		if ((oti->index & 0x1f)==0x10)
-			temp = 0x18;
-		  else
-			temp = oti->regs[oti->index & 0x1f];
+	case 0x3DF:
+		idx = oti->index;
+		if (!oti->chip_id)
+			idx &= 0x1f; 
+		if (idx == 0x10)
+			temp = oti->dipswitch_val;
+		else
+			temp = oti->regs[idx];
 		break;
 
 	default:
@@ -223,7 +298,7 @@ oti_pos_out(uint16_t addr, uint8_t val, void *p)
 {
     oti_t *oti = (oti_t *)p;
 
-    if ((val & 8) != (oti->pos & 8)) {
+    if ((val ^ oti->pos) & 8) {
 	if (val & 8)
 		io_sethandler(0x03c0, 32, oti_in, NULL, NULL,
 			      oti_out, NULL, NULL, oti);
@@ -254,7 +329,7 @@ oti_recalctimings(svga_t *svga)
 
     if (oti->regs[0x0d] & 0x0c) svga->rowoffset <<= 1;
 
-	svga->interlace = oti->regs[0x14] & 0x80;
+    svga->interlace = oti->regs[0x14] & 0x80;
 }
 
 
@@ -267,27 +342,38 @@ oti_init(const device_t *info)
     memset(oti, 0x00, sizeof(oti_t));
     oti->chip_id = info->local;
 
+    oti->dipswitch_val = 0x18;
+
     switch(oti->chip_id) {
-	case 0:
-		romfn = BIOS_37C_PATH;
+	case OTI_037C:
+		romfn = BIOS_037C_PATH;
+		oti->vram_size = 256;
+		oti->regs[0] = 0x08; /* FIXME: The BIOS wants to read this at index 0? This index is undocumented. */
+		/* io_sethandler(0x03c0, 32,
+			      oti_in, NULL, NULL, oti_out, NULL, NULL, oti); */
 		break;		
-		
-	case 3:
-		romfn = BIOS_67_AMA932J_PATH;
+
+	case OTI_067_AMA932J:
+		romfn = BIOS_067_AMA932J_PATH;
+		oti->chip_id = 2;
+		oti->vram_size = 512;
+		oti->dipswitch_val |= 0x20;
+		oti->pos = 0x08;	/* Tell the BIOS the I/O ports are already enabled to avoid a double I/O handler mess. */
+		io_sethandler(0x46e8, 1, oti_pos_in, NULL, NULL, oti_pos_out, NULL, NULL, oti);
 		break;
-	case 2:
-	case 5:
-		romfn = BIOS_77_PATH;
+
+	case OTI_067:
+	case OTI_077:
+		romfn = BIOS_077_PATH;
+		oti->vram_size = device_get_config_int("memory");
+		oti->pos = 0x08;	/* Tell the BIOS the I/O ports are already enabled to avoid a double I/O handler mess. */
+		io_sethandler(0x46e8, 1, oti_pos_in, NULL, NULL, oti_pos_out, NULL, NULL, oti);
 		break;
     }
 
-    if (oti->chip_id == 3)
-	oti->chip_id = 2;
-
     rom_init(&oti->bios_rom, romfn,
 	     0xc0000, 0x8000, 0x7fff, 0, MEM_MAPPING_EXTERNAL);
 
-    oti->vram_size = device_get_config_int("memory");
     oti->vram_mask = (oti->vram_size << 10) - 1;
 
     video_inform(VIDEO_FLAG_TYPE_SPECIAL, &timing_oti);
@@ -297,12 +383,9 @@ oti_init(const device_t *info)
 
     io_sethandler(0x03c0, 32,
 		  oti_in, NULL, NULL, oti_out, NULL, NULL, oti);
-    io_sethandler(0x46e8, 1, oti_pos_in,NULL,NULL, oti_pos_out,NULL,NULL, oti);
 
     oti->svga.miscout = 1;
 
-    oti->regs[0] = 0x08; /* fixme: bios wants to read this at index 0? this index is undocumented */
-
     return(oti);
 }
 
@@ -339,19 +422,19 @@ oti_force_redraw(void *p)
 static int
 oti037c_available(void)
 {
-    return(rom_present(BIOS_37C_PATH));
+    return(rom_present(BIOS_037C_PATH));
 }
 
 static int
 oti067_ama932j_available(void)
 {
-    return(rom_present(BIOS_67_AMA932J_PATH));
+    return(rom_present(BIOS_067_AMA932J_PATH));
 }
 
 static int
 oti067_077_available(void)
 {
-    return(rom_present(BIOS_77_PATH));
+    return(rom_present(BIOS_077_PATH));
 }
 
 
@@ -409,8 +492,7 @@ const device_t oti037c_device =
 	oti_init, oti_close, NULL,
 	oti037c_available,
 	oti_speed_changed,
-	oti_force_redraw,
-	oti067_config
+	oti_force_redraw
 };
 
 const device_t oti067_device =
@@ -433,8 +515,7 @@ const device_t oti067_ama932j_device =
 	oti_init, oti_close, NULL,
 	oti067_ama932j_available,
 	oti_speed_changed,
-	oti_force_redraw,
-	oti067_config
+	oti_force_redraw
 };
 
 const device_t oti077_device =
diff --git a/src/video/vid_svga.c b/src/video/vid_svga.c
index 1621c48f0..c259d77db 100644
--- a/src/video/vid_svga.c
+++ b/src/video/vid_svga.c
@@ -11,7 +11,7 @@
  *		This is intended to be used by another SVGA driver,
  *		and not as a card in it's own right.
  *
- * Version:	@(#)vid_svga.c	1.0.33	2018/10/04
+ * Version:	@(#)vid_svga.c	1.0.34	2018/10/07
  *
  * Authors:	Sarah Walker, <http://pcem-emulator.co.uk/>
  *		Miran Grca, <mgrca8@gmail.com>
@@ -348,7 +348,6 @@ svga_in(uint16_t addr, void *p)
 		break;
 	case 0x3da:
 		svga->attrff = 0;
-		svga->attrff = 0;
 
 		if (svga->cgastat & 0x01)
 			svga->cgastat &= ~0x30;
@@ -789,6 +788,7 @@ svga_init(svga_t *svga, void *p, int memsize,
     svga->vram_display_mask = svga->vram_mask = memsize - 1;
     svga->decode_mask = 0x7fffff;
     svga->changedvram = malloc(memsize >> 12);
+    svga->changedvram = malloc(0x800000 >> 12);
     svga->recalctimings_ex = recalctimings_ex;
     svga->video_in  = video_in;
     svga->video_out = video_out;