diff --git a/source/NTSC.cpp b/source/NTSC.cpp
index e9fc3171..2ac66dc9 100644
--- a/source/NTSC.cpp
+++ b/source/NTSC.cpp
@@ -1306,7 +1306,7 @@ void updateScreenDoubleHires80RGB (long cycles6502 ) // wsUpdateVideoDblHires
 					int width = UpdateDHiRes160Cell(g_nVideoClockHorz-VIDEO_SCANNER_HORZ_START, g_nVideoClockVert, addr, g_pVideoAddress);
 					g_pVideoAddress += width;
 				}
-				else if (RGB_Is560Mode())// || (RGB_IsMixMode() && !((a | m) & 0x80)))
+				else if (RGB_Is560Mode())
 				{
 					update7MonoPixels(a);
 					update7MonoPixels(m);
@@ -1463,7 +1463,9 @@ void updateScreenDoubleLores80 (long cycles6502) // wsUpdateVideoDblLores
 }
 
 //===========================================================================
-static void updateScreenSingleHires40Simplified (long cycles6502)
+
+// Handles both the "SingleHires40" & "DoubleHires40" cases, via UpdateHiResCell()
+static void updateScreenHires40Simplified (long cycles6502)
 {
 	if (g_nVideoMixed && g_nVideoClockVert >= VIDEO_SCANNER_Y_MIXED)
 	{
@@ -1482,24 +1484,8 @@ static void updateScreenSingleHires40Simplified (long cycles6502)
 			else if (g_nVideoClockHorz >= VIDEO_SCANNER_HORZ_START)
 			{
 				uint16_t addr = getVideoScannerAddressHGR();
-
-				if (!RGB_Is560Mode())
-				{
-					UpdateHiResCell(g_nVideoClockHorz-VIDEO_SCANNER_HORZ_START, g_nVideoClockVert, addr, g_pVideoAddress);
-					g_pVideoAddress += 14;
-				}
-				else	// Color Burst is off - duplicate code from updateScreenSingleHires40() (GH#631)
-				{
-					uint8_t *pMain = MemGetMainPtr(addr);
-					uint8_t  m     = pMain[0];
-					uint16_t bits  = g_aPixelDoubleMaskHGR[m & 0x7F]; // Optimization: hgrbits second 128 entries are mirror of first 128
-					if (m & 0x80)
-						bits = (bits << 1) | g_nLastColumnPixelNTSC;
-					updatePixels( bits );
-
-					if (g_nVideoClockHorz == (VIDEO_SCANNER_MAX_HORZ-1))
-						g_nLastColumnPixelNTSC = 0;
-				}
+				UpdateHiResCell(g_nVideoClockHorz-VIDEO_SCANNER_HORZ_START, g_nVideoClockVert, addr, g_pVideoAddress);
+				g_pVideoAddress += 14;
 			}
 		}
 		updateVideoScannerHorzEOLSimple();
@@ -2053,13 +2039,18 @@ void NTSC_SetVideoMode( uint32_t uVideoModeFlags, bool bDelay/*=false*/ )
 			}
 			else
 			{
-				g_pFuncUpdateGraphicsScreen = updateScreenDoubleHires40;
+				if (g_eVideoType == VT_COLOR_MONITOR_RGB)
+					g_pFuncUpdateGraphicsScreen = updateScreenHires40Simplified;	// handles both Single/Double Hires40 (EG. FT's DIGIDREAM demo)
+//				else if (g_eVideoType == VT_COLOR_VIDEOCARD_RGB)
+//					// TODO
+				else
+					g_pFuncUpdateGraphicsScreen = updateScreenDoubleHires40;
 			}
 		}
 		else
 		{
 			if (g_eVideoType == VT_COLOR_MONITOR_RGB)
-				g_pFuncUpdateGraphicsScreen = updateScreenSingleHires40Simplified;
+				g_pFuncUpdateGraphicsScreen = updateScreenHires40Simplified;
 			else if (g_eVideoType == VT_COLOR_VIDEOCARD_RGB)
 				g_pFuncUpdateGraphicsScreen = updateScreenSingleHires40RGB;
 			else
diff --git a/source/RGBMonitor.cpp b/source/RGBMonitor.cpp
index ac631e3b..eddebbd8 100644
--- a/source/RGBMonitor.cpp
+++ b/source/RGBMonitor.cpp
@@ -587,7 +587,7 @@ static void CopySource(int w, int h, int sx, int sy, bgra_t *pVideoAddress, cons
 
 //===========================================================================
 
-#define HIRES_COLUMN_OFFSET (((byteval1 & 0xE0) << 2) | ((byteval3 & 0x03) << 5))	// (prevHighBit | last 2 pixels | next 2 pixesl) * HIRES_COLUMN_UNIT_SIZE
+#define HIRES_COLUMN_OFFSET (((byteval1 & 0xE0) << 2) | ((byteval3 & 0x03) << 5))	// (prevHighBit | last 2 pixels | next 2 pixels) * HIRES_COLUMN_UNIT_SIZE
 
 void UpdateHiResCell (int x, int y, uint16_t addr, bgra_t *pVideoAddress)
 {
@@ -596,6 +596,13 @@ void UpdateHiResCell (int x, int y, uint16_t addr, bgra_t *pVideoAddress)
 	BYTE byteval2 =            *(pMain);
 	BYTE byteval3 = (x < 39) ? *(pMain+1) : 0;
 
+	if (g_uVideoMode & VF_DHIRES)	// ie. VF_DHIRES=1, VF_HIRES=1, VF_80COL=0 - NTSC.cpp refers to this as "DoubleHires40"
+	{
+		byteval1 &= 0x7f;
+		byteval2 &= 0x7f;
+		byteval3 &= 0x7f;
+	}
+
 	if (IsVideoStyle(VS_COLOR_VERTICAL_BLEND))
 	{
 		CopyMixedSource(x, y, SRCOFFS_HIRES+HIRES_COLUMN_OFFSET+((x & 1)*HIRES_COLUMN_SUBUNIT_SIZE), (int)byteval2, pVideoAddress);