diff --git a/src/boards/15.cpp b/src/boards/15.cpp
index 5465a381..01f55cd5 100644
--- a/src/boards/15.cpp
+++ b/src/boards/15.cpp
@@ -55,23 +55,19 @@ static void Sync(void) {
 		}
 		break;
 	}
+	setchr8(0);
 }
 
 static DECLFW(M15Write) {
 	latchea = A;
 	latched = V;
-	switch (latchea & 3) {
-	case 0:
-	case 3:
+	// cah4e3 02.10.19 once again, there may be either two similar mapper 15 exist. the one for 110in1 or 168in1 carts with complex multi game features.
+	// and another implified version for subor/waixing chinese originals and hacks with no different modes, working only in mode 0 and which does not
+	// expect there is any CHR write protection. protecting CHR writes only for mode 3 fixes the problem, all roms may be run on the same source again.
+	if((latchea & 3) == 3)
 		SetupCartCHRMapping(0, CHRptr[0], 0x2000, 0);
-		setchr8(0);
-		break;
-	case 1:
-	case 2:
+	else
 		SetupCartCHRMapping(0, CHRptr[0], 0x2000, 1);
-		setchr8(0);
-		break;
-	}
 	Sync();
 }