diff --git a/Outputs/CRT/Internals/CRTConstants.hpp b/Outputs/CRT/Internals/CRTConstants.hpp
index f17ac438b..5d17b5ad3 100644
--- a/Outputs/CRT/Internals/CRTConstants.hpp
+++ b/Outputs/CRT/Internals/CRTConstants.hpp
@@ -33,7 +33,7 @@ const GLsizei SourceVertexSize = 16;
 
 // These constants hold the size of the rolling buffer to which the CPU writes
 const GLsizei InputBufferBuilderWidth = 2048;
-const GLsizei InputBufferBuilderHeight = 8;
+const GLsizei InputBufferBuilderHeight = 8192;
 
 // This is the size of the intermediate buffers used during composite to RGB conversion
 const GLsizei IntermediateBufferWidth = 2048;
diff --git a/Outputs/CRT/Internals/CRTInputBufferBuilder.cpp b/Outputs/CRT/Internals/CRTInputBufferBuilder.cpp
index 806c5b515..c4d6784c3 100644
--- a/Outputs/CRT/Internals/CRTInputBufferBuilder.cpp
+++ b/Outputs/CRT/Internals/CRTInputBufferBuilder.cpp
@@ -16,8 +16,6 @@ CRTInputBufferBuilder::CRTInputBufferBuilder(size_t bytes_per_pixel) :
 	_bytes_per_pixel(bytes_per_pixel),
 	_next_write_x_position(0),
 	_next_write_y_position(0),
-	_last_uploaded_line(0),
-	_is_full(false),
 	_image(new uint8_t[bytes_per_pixel * InputBufferBuilderWidth * InputBufferBuilderHeight])
 {}
 
@@ -28,7 +26,7 @@ CRTInputBufferBuilder::~CRTInputBufferBuilder()
 
 void CRTInputBufferBuilder::allocate_write_area(size_t required_length)
 {
-	if(!_is_full)
+	if(_next_write_y_position != InputBufferBuilderHeight)
 	{
 		_last_allocation_amount = required_length;
 
@@ -37,8 +35,7 @@ void CRTInputBufferBuilder::allocate_write_area(size_t required_length)
 			_next_write_x_position = 0;
 			_next_write_y_position++;
 
-			_is_full = (_next_write_y_position == _last_uploaded_line + InputBufferBuilderHeight);
-			if(_is_full)
+			if(_next_write_y_position == InputBufferBuilderHeight)
 				return;
 		}
 
@@ -46,12 +43,17 @@ void CRTInputBufferBuilder::allocate_write_area(size_t required_length)
 		_write_y_position = _next_write_y_position;
 		_write_target_pointer = (_write_y_position * InputBufferBuilderWidth) + _write_x_position;
 		_next_write_x_position += required_length + 2;
+
+		if(_write_y_position == 0 && _write_x_position == 0)
+		{
+			memset(_image, 0, _bytes_per_pixel * InputBufferBuilderWidth * InputBufferBuilderHeight);
+		}
 	}
 }
 
 bool CRTInputBufferBuilder::reduce_previous_allocation_to(size_t actual_length)
 {
-	if(_is_full) return false;
+	if(_next_write_y_position == InputBufferBuilderHeight) return false;
 
 	// book end the allocation with duplicates of the first and last pixel, to protect
 	// against rounding errors when this run is drawn
@@ -76,15 +78,14 @@ uint8_t *CRTInputBufferBuilder::get_image_pointer()
 
 uint16_t CRTInputBufferBuilder::get_and_finalise_current_line()
 {
-	uint16_t result = _write_y_position;
+	uint16_t result = _write_y_position + (_next_write_x_position ? 1 : 0);
 	_next_write_x_position = _next_write_y_position = 0;
-	_is_full = false;
 	return result;
 }
 
 uint8_t *CRTInputBufferBuilder::get_write_target()
 {
-	return _is_full ? nullptr : &_image[_write_target_pointer * _bytes_per_pixel];
+	return (_next_write_y_position == InputBufferBuilderHeight) ? nullptr : &_image[_write_target_pointer * _bytes_per_pixel];
 }
 
 uint16_t CRTInputBufferBuilder::get_last_write_x_position()
@@ -94,7 +95,7 @@ uint16_t CRTInputBufferBuilder::get_last_write_x_position()
 
 uint16_t CRTInputBufferBuilder::get_last_write_y_position()
 {
-	return _write_y_position % InputBufferBuilderHeight;
+	return _write_y_position;
 }
 
 size_t CRTInputBufferBuilder::get_bytes_per_pixel()
diff --git a/Outputs/CRT/Internals/CRTInputBufferBuilder.hpp b/Outputs/CRT/Internals/CRTInputBufferBuilder.hpp
index 32346dff0..33279f7c0 100644
--- a/Outputs/CRT/Internals/CRTInputBufferBuilder.hpp
+++ b/Outputs/CRT/Internals/CRTInputBufferBuilder.hpp
@@ -51,11 +51,7 @@ struct CRTInputBufferBuilder {
 		// the buffer size
 		size_t _bytes_per_pixel;
 
-		// Storage for the amount of buffer uploaded so far; initialised correctly by the buffer
-		// builder but otherwise entrusted to the CRT to update.
-		unsigned int _last_uploaded_line;
-		bool _is_full;
-
+		// the buffer
 		uint8_t *_image;
 };