diff --git a/OSBindings/Mac/Clock Signal.xcodeproj/project.pbxproj b/OSBindings/Mac/Clock Signal.xcodeproj/project.pbxproj
index 1aafde12b..4e3de67d9 100644
--- a/OSBindings/Mac/Clock Signal.xcodeproj/project.pbxproj	
+++ b/OSBindings/Mac/Clock Signal.xcodeproj/project.pbxproj	
@@ -47,6 +47,7 @@
 		4B4DC8211D2C2425003C5BF8 /* Vic20.cpp in Sources */ = {isa = PBXBuildFile; fileRef = 4B4DC81F1D2C2425003C5BF8 /* Vic20.cpp */; };
 		4B4DC8281D2C2470003C5BF8 /* C1540.cpp in Sources */ = {isa = PBXBuildFile; fileRef = 4B4DC8261D2C2470003C5BF8 /* C1540.cpp */; };
 		4B4DC82B1D2C27A4003C5BF8 /* SerialBus.cpp in Sources */ = {isa = PBXBuildFile; fileRef = 4B4DC8291D2C27A4003C5BF8 /* SerialBus.cpp */; };
+		4B5073071DDD3B9400C48FBD /* ArrayBuilder.cpp in Sources */ = {isa = PBXBuildFile; fileRef = 4B5073051DDD3B9400C48FBD /* ArrayBuilder.cpp */; };
 		4B55CE5D1C3B7D6F0093A61B /* CSOpenGLView.m in Sources */ = {isa = PBXBuildFile; fileRef = 4B55CE5C1C3B7D6F0093A61B /* CSOpenGLView.m */; };
 		4B55CE5F1C3B7D960093A61B /* MachineDocument.swift in Sources */ = {isa = PBXBuildFile; fileRef = 4B55CE5E1C3B7D960093A61B /* MachineDocument.swift */; };
 		4B59199C1DAC6C46005BB85C /* OricTAP.cpp in Sources */ = {isa = PBXBuildFile; fileRef = 4B59199A1DAC6C46005BB85C /* OricTAP.cpp */; };
@@ -486,6 +487,8 @@
 		4B4DC8271D2C2470003C5BF8 /* C1540.hpp */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.cpp.h; path = C1540.hpp; sourceTree = "<group>"; };
 		4B4DC8291D2C27A4003C5BF8 /* SerialBus.cpp */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.cpp.cpp; path = SerialBus.cpp; sourceTree = "<group>"; };
 		4B4DC82A1D2C27A4003C5BF8 /* SerialBus.hpp */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.cpp.h; path = SerialBus.hpp; sourceTree = "<group>"; };
+		4B5073051DDD3B9400C48FBD /* ArrayBuilder.cpp */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.cpp.cpp; path = ArrayBuilder.cpp; sourceTree = "<group>"; };
+		4B5073061DDD3B9400C48FBD /* ArrayBuilder.hpp */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.cpp.h; path = ArrayBuilder.hpp; sourceTree = "<group>"; };
 		4B55CE5B1C3B7D6F0093A61B /* CSOpenGLView.h */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.h; path = CSOpenGLView.h; sourceTree = "<group>"; };
 		4B55CE5C1C3B7D6F0093A61B /* CSOpenGLView.m */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.objc; path = CSOpenGLView.m; sourceTree = "<group>"; };
 		4B55CE5E1C3B7D960093A61B /* MachineDocument.swift */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.swift; path = MachineDocument.swift; sourceTree = "<group>"; };
@@ -1687,16 +1690,18 @@
 		4BBF99071C8FBA6F0075DAFB /* Internals */ = {
 			isa = PBXGroup;
 			children = (
-				4BC3B74C1CD194CC00F86E85 /* Shaders */,
-				4BBF99081C8FBA6F0075DAFB /* TextureBuilder.cpp */,
-				4BBF99091C8FBA6F0075DAFB /* TextureBuilder.hpp */,
+				4B5073051DDD3B9400C48FBD /* ArrayBuilder.cpp */,
 				4BBF990A1C8FBA6F0075DAFB /* CRTOpenGL.cpp */,
+				4BBF99081C8FBA6F0075DAFB /* TextureBuilder.cpp */,
+				4BBF99121C8FBA6F0075DAFB /* TextureTarget.cpp */,
+				4B5073061DDD3B9400C48FBD /* ArrayBuilder.hpp */,
+				4B0B6E121C9DBD5D00FFB60D /* CRTConstants.hpp */,
 				4BBF990B1C8FBA6F0075DAFB /* CRTOpenGL.hpp */,
 				4BBF990E1C8FBA6F0075DAFB /* Flywheel.hpp */,
 				4BBF990F1C8FBA6F0075DAFB /* OpenGL.hpp */,
-				4BBF99121C8FBA6F0075DAFB /* TextureTarget.cpp */,
+				4BBF99091C8FBA6F0075DAFB /* TextureBuilder.hpp */,
 				4BBF99131C8FBA6F0075DAFB /* TextureTarget.hpp */,
-				4B0B6E121C9DBD5D00FFB60D /* CRTConstants.hpp */,
+				4BC3B74C1CD194CC00F86E85 /* Shaders */,
 			);
 			path = Internals;
 			sourceTree = "<group>";
@@ -1704,12 +1709,12 @@
 		4BC3B74C1CD194CC00F86E85 /* Shaders */ = {
 			isa = PBXGroup;
 			children = (
-				4BC3B74D1CD194CC00F86E85 /* Shader.cpp */,
-				4BC3B74E1CD194CC00F86E85 /* Shader.hpp */,
-				4BC3B7501CD1956900F86E85 /* OutputShader.cpp */,
-				4BC3B7511CD1956900F86E85 /* OutputShader.hpp */,
 				4BBB142F1CD2CECE00BDB55C /* IntermediateShader.cpp */,
+				4BC3B7501CD1956900F86E85 /* OutputShader.cpp */,
+				4BC3B74D1CD194CC00F86E85 /* Shader.cpp */,
 				4BBB14301CD2CECE00BDB55C /* IntermediateShader.hpp */,
+				4BC3B7511CD1956900F86E85 /* OutputShader.hpp */,
+				4BC3B74E1CD194CC00F86E85 /* Shader.hpp */,
 			);
 			path = Shaders;
 			sourceTree = "<group>";
@@ -2353,6 +2358,7 @@
 				4BA22B071D8817CE0008C640 /* Disk.cpp in Sources */,
 				4BC3B7521CD1956900F86E85 /* OutputShader.cpp in Sources */,
 				4B4C83701D4F623200CD541F /* D64.cpp in Sources */,
+				4B5073071DDD3B9400C48FBD /* ArrayBuilder.cpp in Sources */,
 				4B14145B1B58879D00E04248 /* CPU6502.cpp in Sources */,
 				4BEE0A6F1D72496600532C7B /* Cartridge.cpp in Sources */,
 				4B8805FB1DCFF807003085B1 /* Oric.cpp in Sources */,
diff --git a/Outputs/CRT/Internals/ArrayBuilder.cpp b/Outputs/CRT/Internals/ArrayBuilder.cpp
new file mode 100644
index 000000000..dd7057e63
--- /dev/null
+++ b/Outputs/CRT/Internals/ArrayBuilder.cpp
@@ -0,0 +1,10 @@
+//
+//  ArrayBuilder.cpp
+//  Clock Signal
+//
+//  Created by Thomas Harte on 17/11/2016.
+//  Copyright © 2016 Thomas Harte. All rights reserved.
+//
+
+#include "ArrayBuilder.hpp"
+
diff --git a/Outputs/CRT/Internals/ArrayBuilder.hpp b/Outputs/CRT/Internals/ArrayBuilder.hpp
new file mode 100644
index 000000000..97a7b2b63
--- /dev/null
+++ b/Outputs/CRT/Internals/ArrayBuilder.hpp
@@ -0,0 +1,45 @@
+//
+//  ArrayBuilder.hpp
+//  Clock Signal
+//
+//  Created by Thomas Harte on 17/11/2016.
+//  Copyright © 2016 Thomas Harte. All rights reserved.
+//
+
+#ifndef ArrayBuilder_hpp
+#define ArrayBuilder_hpp
+
+#include <vector>
+#include <mutex>
+
+#include "OpenGL.hpp"
+
+namespace Outputs {
+namespace CRT {
+
+class ArrayBuilder {
+	public:
+		ArrayBuilder();
+		virtual ~ArrayBuilder();
+
+		uint8_t *get_input_storage(size_t size);
+		uint8_t *get_output_storage(size_t size);
+		void flush_storage();
+
+		void bind_input();
+		void bind_output();
+		void submit();
+
+	private:
+		struct {
+			std::vector<uint8_t> data;
+			size_t allocated_data, completed_data;
+			GLuint buffer;
+		} output_, input_;
+		std::mutex buffer_mutex_;
+};
+
+}
+}
+
+#endif /* ArrayBuilder_hpp */