diff --git a/source/NTSC.cpp b/source/NTSC.cpp
index fab93fbe..cc3a4258 100644
--- a/source/NTSC.cpp
+++ b/source/NTSC.cpp
@@ -1470,8 +1470,6 @@ void NTSC_SetVideoTextMode( int cols )
 //===========================================================================
 void NTSC_SetVideoMode( uint32_t uVideoModeFlags )
 {
-	int h = g_nVideoClockHorz;
-
 	g_nVideoMixed   = uVideoModeFlags & VF_MIXED;
 	g_nVideoCharSet = VideoGetSWAltCharSet() ? 1 : 0;
 
@@ -1781,8 +1779,17 @@ void NTSC_VideoRedrawWholeScreen( void )
 	const uint16_t currVideoClockHorz = g_nVideoClockHorz;
 #endif
 
+	// (GH#405) For full-speed: whole screen updates will occur periodically
+	// . The V/H pos will have been recalc'ed, so won't be continuous from previous (whole screen) update
+	// . So the redraw must start at H-pos=0 & with the usual reinit for the start of a new line
+	const uint16_t horz = g_nVideoClockHorz;
+	g_nVideoClockHorz = 0;
+	updateVideoScannerAddress();
+
 	VideoUpdateCycles(VIDEO_SCANNER_6502_CYCLES);
 
+	VideoUpdateCycles(horz);	// Finally update to get to correct H-pos
+
 #ifdef _DEBUG
 	_ASSERT(currVideoClockVert == g_nVideoClockVert);
 	_ASSERT(currVideoClockHorz == g_nVideoClockHorz);
diff --git a/source/Video.cpp b/source/Video.cpp
index ef47b341..9204a4e3 100644
--- a/source/Video.cpp
+++ b/source/Video.cpp
@@ -983,21 +983,15 @@ void VideoDisplayLogo ()
 
 //===========================================================================
 
-// AZTEC.DSK: From boot to 'Press any key' (Release build)
-// . 66s always update every frame
-// . 15s only update if any video memory (main/aux, text/hgr, pages1&2) has changed
-// . 10s only update if HIRES changes (17s for Debug build)
-// . ~9s no update during full-speed (but IBIZA.DSK doesn't show anything!)
-
 void VideoRedrawScreenDuringFullSpeed(DWORD dwCyclesThisFrame, bool bInit /*=false*/)
 {
 	static DWORD dwFullSpeedStartTime = 0;
-	static bool bValid = false;
+//	static bool bValid = false;
 
 	if (bInit)
 	{
 		// Just entered full-speed mode
-		bValid = false;
+//		bValid = false;
 		dwFullSpeedStartTime = GetTickCount();
 		return;
 	}
@@ -1010,6 +1004,7 @@ void VideoRedrawScreenDuringFullSpeed(DWORD dwCyclesThisFrame, bool bInit /*=fal
 
 	//
 
+#if 0
 	static BYTE text_main[1024*2] = {0};	// page1 & 2
 	static BYTE text_aux[1024*2] = {0};		// page1 & 2
 	static BYTE hgr_main[8192*2] = {0};		// page1 & 2
@@ -1047,6 +1042,9 @@ void VideoRedrawScreenDuringFullSpeed(DWORD dwCyclesThisFrame, bool bInit /*=fal
 	memcpy(hgr_aux,   MemGetAuxPtr(0x2000),  sizeof(hgr_aux));
 
 	bValid = true;
+#else
+	VideoRedrawScreenAfterFullSpeed(dwCyclesThisFrame);
+#endif
 }
 
 //===========================================================================