diff --git a/Components/6560/6560.cpp b/Components/6560/6560.cpp
index 78fc24e97..d9a4dc183 100644
--- a/Components/6560/6560.cpp
+++ b/Components/6560/6560.cpp
@@ -163,6 +163,7 @@ void MOS6560::output_border(unsigned int number_of_cycles)
 	uint8_t *colour_pointer = _crt->allocate_write_area(1);
 	if(colour_pointer) *colour_pointer = _registers.borderColour;
 	_crt->output_level(number_of_cycles);
+//	_crt->output_blank(number_of_cycles);
 }
 
 uint16_t MOS6560::get_address()
diff --git a/Outputs/CRT/Internals/CRTConstants.hpp b/Outputs/CRT/Internals/CRTConstants.hpp
index d0e3b1c78..0951d65f3 100644
--- a/Outputs/CRT/Internals/CRTConstants.hpp
+++ b/Outputs/CRT/Internals/CRTConstants.hpp
@@ -41,7 +41,10 @@ const GLsizei IntermediateBufferHeight = 1024;
 
 // Some internal buffer sizes
 const GLsizeiptr OutputVertexBufferDataSize = OutputVertexSize * IntermediateBufferHeight;		// i.e. the maximum number of scans of output that can be created between draws
-const GLsizeiptr SourceVertexBufferDataSize = SourceVertexSize * IntermediateBufferHeight * 2;	// (the maximum number of scans) * conservative, high guess at a maximumum number of events likely to occur within a scan
+const GLsizeiptr SourceVertexBufferDataSize = SourceVertexSize * IntermediateBufferHeight * 10;	// (the maximum number of scans) * conservative, high guess at a maximumum number of events likely to occur within a scan
+
+// TODO: when SourceVertexBufferDataSize is exhausted, the CRT keeps filling OutputVertexBufferDataSize regardless,
+// leading to empty scanlines that nevertheless clear old contents.
 
 }
 }
diff --git a/Outputs/CRT/Internals/CRTOpenGL.cpp b/Outputs/CRT/Internals/CRTOpenGL.cpp
index 66a5f9a96..75a27fd1d 100644
--- a/Outputs/CRT/Internals/CRTOpenGL.cpp
+++ b/Outputs/CRT/Internals/CRTOpenGL.cpp
@@ -334,8 +334,10 @@ void OpenGLOutputBuilder::draw_frame(unsigned int output_width, unsigned int out
 
 	glActiveTexture(pixel_accumulation_texture_unit);
 	framebuffer->bind_texture();
-//	compositeTexture->bind_texture();
 	framebuffer->draw((float)output_width / (float)output_height);
+//	glViewport(0, 0, (GLsizei)output_width / 4, (GLsizei)output_height / 4);
+//	compositeTexture->bind_texture();
+//	compositeTexture->draw((float)output_width / (float)output_height);
 
 	_fence = glFenceSync(GL_SYNC_GPU_COMMANDS_COMPLETE, 0);
 	_draw_mutex->unlock();