diff --git a/GPU/Software/Clipper.cpp b/GPU/Software/Clipper.cpp
index deb78c5430..72859b71c0 100644
--- a/GPU/Software/Clipper.cpp
+++ b/GPU/Software/Clipper.cpp
@@ -218,11 +218,15 @@ void ProcessRect(const VertexData& v0, const VertexData& v1)
 
 		RotateUVThrough(v0, v1, *topright, *bottomleft);
 
-		// Four triangles to do backfaces as well. Two of them will get backface culled.
-		Rasterizer::DrawTriangle(*topleft, *topright, *bottomright);
-		Rasterizer::DrawTriangle(*bottomright, *topright, *topleft);
-		Rasterizer::DrawTriangle(*bottomright, *bottomleft, *topleft);
-		Rasterizer::DrawTriangle(*topleft, *bottomleft, *bottomright);
+		if (gstate.isModeClear()) {
+			Rasterizer::ClearRectangle(v0, v1);
+		} else {
+			// Four triangles to do backfaces as well. Two of them will get backface culled.
+			Rasterizer::DrawTriangle(*topleft, *topright, *bottomright);
+			Rasterizer::DrawTriangle(*bottomright, *topright, *topleft);
+			Rasterizer::DrawTriangle(*bottomright, *bottomleft, *topleft);
+			Rasterizer::DrawTriangle(*topleft, *bottomleft, *bottomright);
+		}
 	}
 }
 
diff --git a/GPU/Software/Rasterizer.cpp b/GPU/Software/Rasterizer.cpp
index 3d23904bea..1f7c66c3ee 100644
--- a/GPU/Software/Rasterizer.cpp
+++ b/GPU/Software/Rasterizer.cpp
@@ -1476,6 +1476,138 @@ void DrawPoint(const VertexData &v0)
 	}
 }
 
+void ClearRectangle(const VertexData &v0, const VertexData &v1)
+{
+	int minX = std::min(v0.screenpos.x, v1.screenpos.x) & ~0xF;
+	int minY = std::min(v0.screenpos.y, v1.screenpos.y) & ~0xF;
+	int maxX = (std::max(v0.screenpos.x, v1.screenpos.x) + 0xF) & ~0xF;
+	int maxY = (std::max(v0.screenpos.y, v1.screenpos.y) + 0xF) & ~0xF;
+
+	DrawingCoords scissorTL(gstate.getScissorX1(), gstate.getScissorY1(), 0);
+	DrawingCoords scissorBR(gstate.getScissorX2(), gstate.getScissorY2(), 0);
+	minX = std::max(minX, (int)TransformUnit::DrawingToScreen(scissorTL).x);
+	maxX = std::max(0, std::min(maxX, (int)TransformUnit::DrawingToScreen(scissorBR).x));
+	minY = std::max(minY, (int)TransformUnit::DrawingToScreen(scissorTL).y);
+	maxY = std::max(0, std::min(maxY, (int)TransformUnit::DrawingToScreen(scissorBR).y));
+
+	const int w = (maxX - minX) / 16;
+	if (w <= 0)
+		return;
+
+	if (gstate.isClearModeDepthMask()) {
+		ScreenCoords pprime(minX, minY, 0);
+		const u16 z = v1.screenpos.z;
+		const int stride = gstate.DepthBufStride();
+
+		for (pprime.y = minY; pprime.y < maxY; pprime.y += 16) {
+			DrawingCoords p = TransformUnit::ScreenToDrawing(pprime);
+
+			if ((z & 0xFF) == (z >> 8)) {
+				u16 *row = &depthbuf.as16[p.x + p.y * stride];
+				memset(row, z, w * 2);
+			} else {
+				for (int x = 0; x < w; ++x) {
+					SetPixelDepth(p.x + x, p.y, z);
+				}
+			}
+		}
+	}
+
+	const u32 new_color = v1.color0.ToRGBA();
+	u16 new_color16;
+
+	// Note: this stays 0xFFFFFFFF if keeping color and alpha, even for 16-bit.
+	u32 keepOldMask = 0xFFFFFFFF;
+	switch (gstate.FrameBufFormat()) {
+	case GE_FORMAT_565:
+		new_color16 = RGBA8888ToRGB565(new_color);
+		if (gstate.isClearModeColorMask())
+			keepOldMask = 0;
+		break;
+
+	case GE_FORMAT_5551:
+		new_color16 = RGBA8888ToRGBA5551(new_color);
+		if (gstate.isClearModeColorMask())
+			keepOldMask &= 0x00008000;
+		if (gstate.isClearModeAlphaMask())
+			keepOldMask &= 0x00007FFF;
+		break;
+
+	case GE_FORMAT_4444:
+		new_color16 = RGBA8888ToRGBA4444(new_color);
+		if (gstate.isClearModeColorMask())
+			keepOldMask &= 0x0000F000;
+		if (gstate.isClearModeAlphaMask())
+			keepOldMask &= 0x00000FFF;
+		break;
+
+	case GE_FORMAT_8888:
+		if (gstate.isClearModeColorMask())
+			keepOldMask &= 0xFF000000;
+		if (gstate.isClearModeAlphaMask())
+			keepOldMask &= 0x00FFFFFF;
+		break;
+
+	case GE_FORMAT_INVALID:
+		_dbg_assert_msg_(G3D, false, "Software: invalid framebuf format.");
+		break;
+	}
+
+	if (keepOldMask == 0) {
+		ScreenCoords pprime(minX, minY, 0);
+		const int stride = gstate.FrameBufStride();
+
+		if (gstate.FrameBufFormat() == GE_FORMAT_8888) {
+			for (pprime.y = minY; pprime.y < maxY; pprime.y += 16) {
+				DrawingCoords p = TransformUnit::ScreenToDrawing(pprime);
+				if ((new_color & 0xFF) == (new_color >> 8) && (new_color && 0xFFFF) == (new_color >> 16)) {
+					u32 *row = &fb.as32[p.x + p.y * stride];
+					memset(row, new_color, w * 4);
+				} else {
+					for (int x = 0; x < w; ++x) {
+						fb.Set32(p.x + x, p.y, stride, new_color);
+					}
+				}
+			}
+		} else {
+			for (pprime.y = minY; pprime.y < maxY; pprime.y += 16) {
+				DrawingCoords p = TransformUnit::ScreenToDrawing(pprime);
+				if ((new_color16 & 0xFF) == (new_color16 >> 8)) {
+					u16 *row = &fb.as16[p.x + p.y * stride];
+					memset(row, new_color16, w * 2);
+				} else {
+					for (int x = 0; x < w; ++x) {
+						fb.Set16(p.x + x, p.y, stride, new_color16);
+					}
+				}
+			}
+		}
+	} else if (keepOldMask != 0xFFFFFFFF) {
+		ScreenCoords pprime(minX, minY, 0);
+		const int stride = gstate.FrameBufStride();
+
+		if (gstate.FrameBufFormat() == GE_FORMAT_8888) {
+			for (pprime.y = minY; pprime.y < maxY; pprime.y += 16) {
+				DrawingCoords p = TransformUnit::ScreenToDrawing(pprime);
+				for (int x = 0; x < w; ++x) {
+					const u32 old_color = fb.Get32(p.x + x, p.y, stride);
+					const u32 c = (old_color & keepOldMask) | (new_color & ~keepOldMask);
+					fb.Set32(p.x + x, p.y, stride, c);
+				}
+			}
+		} else {
+			for (pprime.y = minY; pprime.y < maxY; pprime.y += 16) {
+				DrawingCoords p = TransformUnit::ScreenToDrawing(pprime);
+				for (int x = 0; x < w; ++x) {
+					const u16 old_color = fb.Get16(p.x + x, p.y, stride);
+					const u16 c = (old_color & keepOldMask) | (new_color16 & ~keepOldMask);
+					fb.Set16(p.x + x, p.y, stride, c);
+				}
+			}
+		}
+	}
+}
+
 void DrawLine(const VertexData &v0, const VertexData &v1)
 {
 	// TODO: Use a proper line drawing algorithm that handles fractional endpoints correctly.
diff --git a/GPU/Software/Rasterizer.h b/GPU/Software/Rasterizer.h
index ab9c314c91..53d44e8af0 100644
--- a/GPU/Software/Rasterizer.h
+++ b/GPU/Software/Rasterizer.h
@@ -27,6 +27,7 @@ namespace Rasterizer {
 void DrawTriangle(const VertexData& v0, const VertexData& v1, const VertexData& v2);
 void DrawPoint(const VertexData &v0);
 void DrawLine(const VertexData &v0, const VertexData &v1);
+void ClearRectangle(const VertexData &v0, const VertexData &v1);
 
 bool GetCurrentStencilbuffer(GPUDebugBuffer &buffer);
 bool GetCurrentTexture(GPUDebugBuffer &buffer, int level);