diff --git a/src/add-ons/accelerants/common/create_display_modes.cpp b/src/add-ons/accelerants/common/create_display_modes.cpp
index 05b41e2f8f..de211465df 100644
--- a/src/add-ons/accelerants/common/create_display_modes.cpp
+++ b/src/add-ons/accelerants/common/create_display_modes.cpp
@@ -112,10 +112,8 @@ using namespace BPrivate;
 static float
 get_refresh_rate(const display_mode& mode)
 {
-	// we have to be catious as refresh rate cannot be controlled directly,
-	// so it suffers under rounding errors and hardware restrictions
-	return rint(10 * float(mode.timing.pixel_clock * 1000) / 
-		float(mode.timing.h_total * mode.timing.v_total)) / 10.0;
+	return float(mode.timing.pixel_clock * 1000) / 
+		float(mode.timing.h_total * mode.timing.v_total);
 }
 
 
@@ -140,8 +138,7 @@ compare_mode(const void* _mode1, const void* _mode2)
 	if (mode1->space != mode2->space)
 		return mode1->space - mode2->space;
 
-	return (int)(10 * get_refresh_rate(*mode1)
-		-  10 * get_refresh_rate(*mode2));
+	return (int)(100 * (get_refresh_rate(*mode1) - get_refresh_rate(*mode2)));
 }
 
 
@@ -220,9 +217,13 @@ ModeList::AddModes(edid1_info* info)
 		if (info->detailed_monitor[i].monitor_desc_type != EDID1_IS_DETAILED_TIMING)
 			continue;
 
-		// TODO: handle sync and flags correctly!
+		// TODO: handle flags correctly!
 		const edid1_detailed_timing& timing = info->detailed_monitor[i].data.detailed_timing;
 		display_mode mode;
+		
+		if (timing.pixel_clock <= 0 || timing.sync != 3)
+			continue;
+			
 		mode.timing.pixel_clock = timing.pixel_clock * 10;
 		mode.timing.h_display = timing.h_active;
 		mode.timing.h_sync_start = timing.h_active + timing.h_sync_off;
@@ -232,7 +233,13 @@ ModeList::AddModes(edid1_info* info)
 		mode.timing.v_sync_start = timing.v_active + timing.v_sync_off;
 		mode.timing.v_sync_end = mode.timing.v_sync_start + timing.v_sync_width;
 		mode.timing.v_total = timing.v_active + timing.v_blank;
-		mode.timing.flags = POSITIVE_SYNC;
+		mode.timing.flags = 0;
+		if (timing.sync == 3) {
+			if (timing.misc & 1)
+				mode.timing.flags |= B_POSITIVE_HSYNC;
+			if (timing.misc & 2)
+				mode.timing.flags |= B_POSITIVE_VSYNC;
+		}
 		if (timing.interlaced)
 			mode.timing.flags |= B_TIMING_INTERLACED;
 		mode.space = B_RGB32;
@@ -241,6 +248,8 @@ ModeList::AddModes(edid1_info* info)
 		mode.h_display_start = 0;
 		mode.v_display_start = 0;
 		mode.flags = MODE_FLAGS;
+		
+		_AddMode(&mode);
 	}
 	
 	// TODO: add other modes from the base list that satisfy the display's
@@ -315,10 +324,15 @@ ModeList::_AddBaseMode(uint16 width, uint16 height, uint32 refresh)
 	for (uint32 i = 0; i < kNumBaseModes; i++) {
 		const display_mode& mode = kBaseModeList[i];
 
+		// Add mode if width and height match, and the computed refresh rate of
+		// the mode is within 1.2 percent of the refresh rate specified by the
+		// caller.  Note that refresh rates computed from mode parameters is
+		// not exact;  thus, the tolerance of 1.2% was obtained by testing the
+		// various established modes that can be selected by the EDID info.
+		
 		if (mode.timing.h_display == width && mode.timing.v_display == height
-			&& get_refresh_rate(mode) == refresh) {
+			&& fabs(get_refresh_rate(mode) - refresh) < refresh * 0.012) {
 			_AddMode(&mode);
-			return;
 		}
 	}
 }
diff --git a/src/add-ons/accelerants/common/ddc.c b/src/add-ons/accelerants/common/ddc.c
index 411c1abbbf..56b5b28fd0 100644
--- a/src/add-ons/accelerants/common/ddc.c
+++ b/src/add-ons/accelerants/common/ddc.c
@@ -3,9 +3,7 @@
  * Distributed under the terms of the MIT License.
  */
 
-/*!
-	DDC communication
-*/
+/*!	DDC communication */
 
 
 #include "ddc_int.h"
@@ -18,38 +16,44 @@
 #include <stdlib.h>
 
 
-#define READ_RETRIES 4
-	// number of retries to read ddc data
+#define READ_RETRIES 4		// number of retries to read ddc data
 
-#if 0
-/*!	Verify checksum of ddc data
-	(some monitors have a broken checksum - bad luck for them)
-*/
+
+#define TRACE_DDC
+#ifdef TRACE_DDC
+extern void _sPrintf(const char* format, ...);
+#	define TRACE(x...) _sPrintf("DDC: " x)
+#else
+#	define TRACE(x...) ;
+#endif
+
+
+
+//! Verify checksum of DDC data.
 static status_t
 verify_checksum(const uint8 *data, size_t len)
 {
 	uint32 index;
 	uint8 sum = 0;
-	uint8 all_or = 0;
-	
+	uint8 allOr = 0;
+
 	for (index = 0; index < len; ++index, ++data) {
 		sum += *data;
-		all_or |= *data;
+		allOr |= *data;
 	}
-	
-	if (all_or == 0) {
-		SHOW_ERROR0(2, "DDC information contains zeros only");
+
+	if (allOr == 0) {
+		TRACE("verify_checksum() DDC information contains zeros only\n");
 		return B_ERROR;
 	}
-	
+
 	if (sum != 0) {
-		SHOW_ERROR0(2, "Checksum error of DDC information");
+		TRACE("verify_checksum() Checksum error in DDC information\n");
 		return B_IO_ERROR;
 	}
-		
+
 	return B_OK;
 }
-#endif
 
 
 //!	Read ddc2 data from monitor
@@ -66,11 +70,17 @@ ddc2_read(const i2c_bus *bus, int start, uint8 *buffer, size_t length)
 	for (i = 0; i < READ_RETRIES; ++i) {
 		status = i2c_send_receive(bus, 0xa0, writeBuffer,
 			start < 0x100 ? 1 : 2, buffer, length);
-		// don't verify checksum - it's often broken
-		if (status == B_OK /*&& verify_checksum( buffer, len ) == B_OK*/)
-			break;
 
-		status = B_ERROR;
+		if (status != B_OK)
+			TRACE("ddc2_read(): DDC information read failure\n");
+
+		if (status == B_OK) {
+			status = verify_checksum(buffer, length);
+			if (status == B_OK)
+				break;
+
+			dprintf("DDC checksum incorrect!\n");
+		}
 	}
 
 	return status;
@@ -121,6 +131,9 @@ ddc2_read_vdif(const i2c_bus *bus, int start,
 #endif
 
 
+//	#pragma mark -
+
+
 void
 ddc2_init_timing(i2c_bus *bus)
 {
@@ -145,6 +158,11 @@ ddc2_read_edid1(const i2c_bus *bus, edid1_info *edid,
 	if (status != B_OK)
 		return status;
 
+	if (raw.version.version != 1 || raw.version.revision > 4) {
+		TRACE("ddc2_read_edid1() EDID version or revision out of range\n");
+		return B_ERROR;
+	}
+
 	edid_decode(edid, &raw);
 
 	if (vdif != NULL)
diff --git a/src/add-ons/accelerants/common/decode_edid.c b/src/add-ons/accelerants/common/decode_edid.c
index 4fc5f31148..0149dc653e 100644
--- a/src/add-ons/accelerants/common/decode_edid.c
+++ b/src/add-ons/accelerants/common/decode_edid.c
@@ -155,7 +155,7 @@ copy_str(char *dest, const uint8 *src, size_t len)
 	uint32 i;
 
 	// copy until 0xa
-	for (i = 0; i < len; ++i) {
+	for (i = 0; i < len; i++) {
 		if (*src == 0xa)
 			break;
 
@@ -163,12 +163,14 @@ copy_str(char *dest, const uint8 *src, size_t len)
 	}
 
 	// remove trailing spaces
-	for (i = i - 1; i >= 0; --i) {
-		if (*dest-- != ' ')
+	while (i-- > 0) {
+		if (*(dest - 1) != ' ')
 			break;
+
+		dest--;
 	}
 
-	*++dest = 0;
+	*dest = '\0';
 }