diff --git a/CHANGES b/CHANGES
index ddd2aaa6d..71ed6aad1 100644
--- a/CHANGES
+++ b/CHANGES
@@ -82,6 +82,7 @@ Misc:
  - GBA: Allow pausing event loop while CPU is blocked
  - GBA BIOS: Division by zero should emit a FATAL error
  - GBA Video: Convert OpenGL VRAM texture to integer
+ - GBA Video: Improve speed of window texture generation on AMD
  - Debugger: Keep track of global cycle count
  - FFmpeg: Add looping option for GIF/APNG
  - mGUI: Show battery percentage
diff --git a/src/gba/renderers/gl.c b/src/gba/renderers/gl.c
index cc086ba9a..f65f24c77 100644
--- a/src/gba/renderers/gl.c
+++ b/src/gba/renderers/gl.c
@@ -497,7 +497,7 @@ static const char* const _renderWindow =
 	"uniform ivec4 win1[160];\n"
 	"OUT(0) out ivec4 window;\n"
 
-	"void crop(vec4 windowParams, int flags, inout ivec3 windowFlags) {\n"
+	"bool crop(vec4 windowParams) {\n"
 	"	bvec4 compare = lessThan(texCoord.xxyy, windowParams);\n"
 	"	compare = equal(compare, bvec4(true, false, true, false));\n"
 	"	if (any(compare)) {\n"
@@ -505,25 +505,23 @@ static const char* const _renderWindow =
 	"		vec2 v = windowParams.zw;\n"
 	"		if (v.x > v.y) {\n"
 	"			if (compare.z && compare.w) {\n"
-	"				return;\n"
+	"				return false;\n"
 	"			}\n"
 	"		} else if (compare.z || compare.w) {\n"
-	"			return;\n"
+	"			return false;\n"
 	"		}\n"
 	"		if (h.x > h.y) {\n"
 	"			if (compare.x && compare.y) {\n"
-	"				return;\n"
+	"				return false;\n"
 	"			}\n"
 	"		} else if (compare.x || compare.y) {\n"
-	"			return;\n"
+	"			return false;\n"
 	"		}\n"
 	"	}\n"
-	"	windowFlags.x = flags;\n"
+	"	return true;\n"
 	"}\n"
 
-	"vec4 interpolate(ivec4 win[160]) {\n"
-	"	vec4 bottom = vec4(win[int(texCoord.y) - 1]);\n"
-	"	vec4 top = vec4(win[int(texCoord.y)]);\n"
+	"vec4 interpolate(vec4 top, vec4 bottom) {\n"
 	"	if (distance(top, bottom) > 40.) {\n"
 	"		return top;\n"
 	"	}\n"
@@ -535,14 +533,15 @@ static const char* const _renderWindow =
 	"	if ((dispcnt & 0xE0) == 0) {\n"
 	"		window = ivec4(dispflags, blend, 0);\n"
 	"	} else {\n"
-	"		ivec3 windowFlags = ivec3(flags.z, blend);\n"
-	"		if ((dispcnt & 0x40) != 0) { \n"
-	"			crop(interpolate(win1), flags.y, windowFlags);\n"
+	"		ivec4 windowFlags = ivec4(flags.z, blend, 0);\n"
+	"		int top = int(texCoord.y);\n"
+	"		int bottom = max(top - 1, 0);\n"
+	"		if ((dispcnt & 0x20) != 0 && crop(interpolate(vec4(win0[top]), vec4(win0[bottom])))) { \n"
+	"			windowFlags.x = flags.x;\n"
+	"		} else if ((dispcnt & 0x40) != 0 && crop(interpolate(vec4(win1[top]), vec4(win1[bottom])))) {\n"
+	"			windowFlags.x = flags.y;\n"
 	"		}\n"
-	"		if ((dispcnt & 0x20) != 0) { \n"
-	"			crop(interpolate(win0), flags.x, windowFlags);\n"
-	"		}\n"
-	"		window = ivec4(windowFlags, 0);\n"
+	"		window = windowFlags;\n"
 	"	}\n"
 	"}\n";