diff --git a/BizHawk.Emulation/Consoles/Nintendo/GBA/LibMeteor.cs b/BizHawk.Emulation/Consoles/Nintendo/GBA/LibMeteor.cs
index 921fb8917d..8e6b134d63 100644
--- a/BizHawk.Emulation/Consoles/Nintendo/GBA/LibMeteor.cs
+++ b/BizHawk.Emulation/Consoles/Nintendo/GBA/LibMeteor.cs
@@ -250,5 +250,19 @@ namespace BizHawk.Emulation.Consoles.Nintendo.GBA
 		/// <param name="val"></param>
 		[DllImport("libmeteor.dll", CallingConvention = CallingConvention.Cdecl)]
 		public static extern void libmeteor_writebus(uint addr, byte val);
+
+		/// <summary>
+		/// type of the scanline callback
+		/// </summary>
+		[UnmanagedFunctionPointer(CallingConvention.Cdecl)]
+		public delegate void ScanlineCallback();
+
+		/// <summary>
+		/// set a callback to coincide with vcount interrupts
+		/// </summary>
+		/// <param name="callback">null to clear</param>
+		/// <param name="scanline">0-227, 160 occurring first in a frame</param>
+		[DllImport("libmeteor.dll", CallingConvention = CallingConvention.Cdecl)]
+		public static extern void libmeteor_setscanlinecallback(ScanlineCallback callback, int scanline);
 	}
 }
diff --git a/BizHawk.Emulation/Consoles/Nintendo/GBA/Meteor.cs b/BizHawk.Emulation/Consoles/Nintendo/GBA/Meteor.cs
index f0bef366ab..0e624d6883 100644
--- a/BizHawk.Emulation/Consoles/Nintendo/GBA/Meteor.cs
+++ b/BizHawk.Emulation/Consoles/Nintendo/GBA/Meteor.cs
@@ -25,6 +25,8 @@ namespace BizHawk.Emulation.Consoles.Nintendo.GBA
 		{
 			if (bios.Length != 16384)
 				throw new Exception("GBA bios must be exactly 16384 bytes!");
+			if (rom.Length > 32 * 1024 * 1024)
+				throw new Exception("Rom is too big!");
 			Init();
 			LibMeteor.libmeteor_hardreset();
 			LibMeteor.libmeteor_loadbios(bios, (uint)bios.Length);
@@ -46,6 +48,8 @@ namespace BizHawk.Emulation.Consoles.Nintendo.GBA
 				LibMeteor.libmeteor_frameadvance();
 			if (IsLagFrame)
 				LagCount++;
+			if (EndOfFrameCallback != null)
+				EndOfFrameCallback();
 		}
 
 		public int Frame { get; private set; }
@@ -376,6 +380,40 @@ namespace BizHawk.Emulation.Consoles.Nintendo.GBA
 			CoreInputComm.Tracer.Put(msg);
 		}
 
+		Action EndOfFrameCallback = null;
+		LibMeteor.ScanlineCallback scanlinecb = null;
+
+		/// <summary>
+		/// 
+		/// </summary>
+		/// <param name="callback">null to cancel</param>
+		/// <param name="scanline">0-227, null = end of frame</param>
+		public void SetScanlineCallback(Action callback, int? scanline)
+		{
+			if (callback == null)
+			{
+				LibMeteor.libmeteor_setscanlinecallback(null, 400);
+				EndOfFrameCallback = null;
+				scanlinecb = null;
+			}
+			else if (scanline == null)
+			{
+				LibMeteor.libmeteor_setscanlinecallback(null, 400);
+				EndOfFrameCallback = callback;
+				scanlinecb = null;
+			}
+			else if (scanline >= 0 && scanline <= 227)
+			{
+				scanlinecb = new LibMeteor.ScanlineCallback(callback);
+				LibMeteor.libmeteor_setscanlinecallback(scanlinecb, (int)scanline);
+				EndOfFrameCallback = null;
+			}
+			else
+			{
+				throw new ArgumentOutOfRangeException("Scanline must be in [0, 227]!");
+			}
+		}
+
 		void Init()
 		{
 			if (attachedcore != null)
diff --git a/BizHawk.MultiClient/GBAtools/GBAGPUView.Designer.cs b/BizHawk.MultiClient/GBAtools/GBAGPUView.Designer.cs
index 70422c79ae..2b7ab296d1 100644
--- a/BizHawk.MultiClient/GBAtools/GBAGPUView.Designer.cs
+++ b/BizHawk.MultiClient/GBAtools/GBAGPUView.Designer.cs
@@ -32,6 +32,13 @@
 			this.panel1 = new System.Windows.Forms.Panel();
 			this.label1 = new System.Windows.Forms.Label();
 			this.buttonShowWidget = new System.Windows.Forms.Button();
+			this.groupBox1 = new System.Windows.Forms.GroupBox();
+			this.radioButtonFrame = new System.Windows.Forms.RadioButton();
+			this.radioButtonScanline = new System.Windows.Forms.RadioButton();
+			this.radioButtonManual = new System.Windows.Forms.RadioButton();
+			this.hScrollBar1 = new System.Windows.Forms.HScrollBar();
+			this.buttonRefresh = new System.Windows.Forms.Button();
+			this.groupBox1.SuspendLayout();
 			this.SuspendLayout();
 			// 
 			// listBoxWidgets
@@ -72,11 +79,80 @@
 			this.buttonShowWidget.UseVisualStyleBackColor = true;
 			this.buttonShowWidget.Click += new System.EventHandler(this.buttonShowWidget_Click);
 			// 
+			// groupBox1
+			// 
+			this.groupBox1.Controls.Add(this.buttonRefresh);
+			this.groupBox1.Controls.Add(this.hScrollBar1);
+			this.groupBox1.Controls.Add(this.radioButtonManual);
+			this.groupBox1.Controls.Add(this.radioButtonScanline);
+			this.groupBox1.Controls.Add(this.radioButtonFrame);
+			this.groupBox1.Location = new System.Drawing.Point(15, 220);
+			this.groupBox1.Name = "groupBox1";
+			this.groupBox1.Size = new System.Drawing.Size(117, 173);
+			this.groupBox1.TabIndex = 4;
+			this.groupBox1.TabStop = false;
+			this.groupBox1.Text = "Refresh";
+			// 
+			// radioButtonFrame
+			// 
+			this.radioButtonFrame.AutoSize = true;
+			this.radioButtonFrame.Location = new System.Drawing.Point(6, 19);
+			this.radioButtonFrame.Name = "radioButtonFrame";
+			this.radioButtonFrame.Size = new System.Drawing.Size(54, 17);
+			this.radioButtonFrame.TabIndex = 0;
+			this.radioButtonFrame.Text = "Frame";
+			this.radioButtonFrame.UseVisualStyleBackColor = true;
+			this.radioButtonFrame.CheckedChanged += new System.EventHandler(this.radioButtonFrame_CheckedChanged);
+			// 
+			// radioButtonScanline
+			// 
+			this.radioButtonScanline.AutoSize = true;
+			this.radioButtonScanline.Location = new System.Drawing.Point(6, 42);
+			this.radioButtonScanline.Name = "radioButtonScanline";
+			this.radioButtonScanline.Size = new System.Drawing.Size(66, 17);
+			this.radioButtonScanline.TabIndex = 1;
+			this.radioButtonScanline.Text = "Scanline";
+			this.radioButtonScanline.UseVisualStyleBackColor = true;
+			this.radioButtonScanline.CheckedChanged += new System.EventHandler(this.radioButtonScanline_CheckedChanged);
+			// 
+			// radioButtonManual
+			// 
+			this.radioButtonManual.AutoSize = true;
+			this.radioButtonManual.Location = new System.Drawing.Point(6, 81);
+			this.radioButtonManual.Name = "radioButtonManual";
+			this.radioButtonManual.Size = new System.Drawing.Size(60, 17);
+			this.radioButtonManual.TabIndex = 2;
+			this.radioButtonManual.TabStop = true;
+			this.radioButtonManual.Text = "Manual";
+			this.radioButtonManual.UseVisualStyleBackColor = true;
+			this.radioButtonManual.CheckedChanged += new System.EventHandler(this.radioButtonManual_CheckedChanged);
+			// 
+			// hScrollBar1
+			// 
+			this.hScrollBar1.LargeChange = 20;
+			this.hScrollBar1.Location = new System.Drawing.Point(3, 62);
+			this.hScrollBar1.Maximum = 246;
+			this.hScrollBar1.Name = "hScrollBar1";
+			this.hScrollBar1.Size = new System.Drawing.Size(111, 16);
+			this.hScrollBar1.TabIndex = 3;
+			this.hScrollBar1.ValueChanged += new System.EventHandler(this.hScrollBar1_ValueChanged);
+			// 
+			// buttonRefresh
+			// 
+			this.buttonRefresh.Location = new System.Drawing.Point(6, 104);
+			this.buttonRefresh.Name = "buttonRefresh";
+			this.buttonRefresh.Size = new System.Drawing.Size(75, 23);
+			this.buttonRefresh.TabIndex = 4;
+			this.buttonRefresh.Text = "Refresh";
+			this.buttonRefresh.UseVisualStyleBackColor = true;
+			this.buttonRefresh.Click += new System.EventHandler(this.buttonRefresh_Click);
+			// 
 			// GBAGPUView
 			// 
 			this.AutoScaleDimensions = new System.Drawing.SizeF(6F, 13F);
 			this.AutoScaleMode = System.Windows.Forms.AutoScaleMode.Font;
 			this.ClientSize = new System.Drawing.Size(636, 405);
+			this.Controls.Add(this.groupBox1);
 			this.Controls.Add(this.buttonShowWidget);
 			this.Controls.Add(this.label1);
 			this.Controls.Add(this.panel1);
@@ -84,7 +160,10 @@
 			this.Name = "GBAGPUView";
 			this.SizeGripStyle = System.Windows.Forms.SizeGripStyle.Show;
 			this.Text = "GBA GPU Viewer";
+			this.FormClosed += new System.Windows.Forms.FormClosedEventHandler(this.GBAGPUView_FormClosed);
 			this.Load += new System.EventHandler(this.GBAGPUView_Load);
+			this.groupBox1.ResumeLayout(false);
+			this.groupBox1.PerformLayout();
 			this.ResumeLayout(false);
 			this.PerformLayout();
 
@@ -96,6 +175,12 @@
 		private System.Windows.Forms.Panel panel1;
 		private System.Windows.Forms.Label label1;
 		private System.Windows.Forms.Button buttonShowWidget;
+		private System.Windows.Forms.GroupBox groupBox1;
+		private System.Windows.Forms.Button buttonRefresh;
+		private System.Windows.Forms.HScrollBar hScrollBar1;
+		private System.Windows.Forms.RadioButton radioButtonManual;
+		private System.Windows.Forms.RadioButton radioButtonScanline;
+		private System.Windows.Forms.RadioButton radioButtonFrame;
 
 	}
 }
\ No newline at end of file
diff --git a/BizHawk.MultiClient/GBAtools/GBAGPUView.cs b/BizHawk.MultiClient/GBAtools/GBAGPUView.cs
index 734f49fc49..31559a97a4 100644
--- a/BizHawk.MultiClient/GBAtools/GBAGPUView.cs
+++ b/BizHawk.MultiClient/GBAtools/GBAGPUView.cs
@@ -35,6 +35,9 @@ namespace BizHawk.MultiClient.GBAtools
 			Buffer.BlockCopy(tmp, 0, ColorConversion, sizeof(int) * tmp.Length, sizeof(int) * tmp.Length);
 
 			GenerateWidgets();
+			radioButtonFrame.Checked = true;
+			hScrollBar1_ValueChanged(null, null);
+			RecomputeRefresh();
 		}
 
 		#region drawing primitives
@@ -659,7 +662,22 @@ namespace BizHawk.MultiClient.GBAtools
 				return;
 			if (gba != null)
 			{
-				DrawEverything();
+				if (cbscanline_emu != cbscanline)
+				{
+					cbscanline_emu = cbscanline;
+					if (cbscanline == -2) // manual, do nothing
+					{
+						gba.SetScanlineCallback(null, null);
+					}
+					else if (cbscanline == -1) // end of frame
+					{
+						gba.SetScanlineCallback(DrawEverything, null);
+					}
+					else
+					{
+						gba.SetScanlineCallback(DrawEverything, cbscanline);
+					}
+				}
 			}
 		}
 
@@ -688,5 +706,65 @@ namespace BizHawk.MultiClient.GBAtools
 		{
 			ShowSelectedWidget();
 		}
+
+		int cbscanline;
+		int cbscanline_emu = 500;
+
+		void RecomputeRefresh()
+		{
+			if (radioButtonFrame.Checked)
+			{
+				hScrollBar1.Enabled = false;
+				buttonRefresh.Enabled = false;
+				cbscanline = -1;
+			}
+			else if (radioButtonScanline.Checked)
+			{
+				hScrollBar1.Enabled = true;
+				buttonRefresh.Enabled = false;
+				cbscanline = (hScrollBar1.Value + 160) % 228;
+			}
+			else if (radioButtonManual.Checked)
+			{
+				hScrollBar1.Enabled = false;
+				buttonRefresh.Enabled = true;
+				cbscanline = -2;
+			}
+		}
+
+		private void radioButtonFrame_CheckedChanged(object sender, EventArgs e)
+		{
+			RecomputeRefresh();
+		}
+
+		private void radioButtonScanline_CheckedChanged(object sender, EventArgs e)
+		{
+			RecomputeRefresh();
+		}
+
+		private void hScrollBar1_ValueChanged(object sender, EventArgs e)
+		{
+			cbscanline = (hScrollBar1.Value + 160) % 228;
+			radioButtonScanline.Text = "Scanline " + cbscanline;
+		}
+
+		private void radioButtonManual_CheckedChanged(object sender, EventArgs e)
+		{
+			RecomputeRefresh();
+		}
+
+		private void buttonRefresh_Click(object sender, EventArgs e)
+		{
+			DrawEverything();
+		}
+
+		private void GBAGPUView_FormClosed(object sender, FormClosedEventArgs e)
+		{
+			if (gba != null)
+			{
+				gba.SetScanlineCallback(null, null);
+				gba = null;
+			}
+		}
 	}
 }
diff --git a/BizHawk.MultiClient/GBtools/GBGPUView.Designer.cs b/BizHawk.MultiClient/GBtools/GBGPUView.Designer.cs
index 70e64e6ff3..c471265e2c 100644
--- a/BizHawk.MultiClient/GBtools/GBGPUView.Designer.cs
+++ b/BizHawk.MultiClient/GBtools/GBGPUView.Designer.cs
@@ -211,7 +211,7 @@
 			// hScrollBarScanline
 			// 
 			this.hScrollBarScanline.Location = new System.Drawing.Point(76, 45);
-			this.hScrollBarScanline.Maximum = 153;
+			this.hScrollBarScanline.Maximum = 162;
 			this.hScrollBarScanline.Name = "hScrollBarScanline";
 			this.hScrollBarScanline.Size = new System.Drawing.Size(192, 16);
 			this.hScrollBarScanline.TabIndex = 21;
diff --git a/BizHawk.MultiClient/output/dll/libmeteor.dll b/BizHawk.MultiClient/output/dll/libmeteor.dll
index 1f05942894..75ccb90052 100644
Binary files a/BizHawk.MultiClient/output/dll/libmeteor.dll and b/BizHawk.MultiClient/output/dll/libmeteor.dll differ
diff --git a/libmeteor/cinterface.cpp b/libmeteor/cinterface.cpp
index 66b2f93df8..5421b44bb5 100644
--- a/libmeteor/cinterface.cpp
+++ b/libmeteor/cinterface.cpp
@@ -217,3 +217,21 @@ EXPORT void libmeteor_writebus(uint32_t addr, uint8_t val)
 {
 	AMeteor::_memory.Write8(addr, val);
 }
+
+int slcallbackline = 400;
+void (*slcallback)() = NULL;
+
+EXPORT void libmeteor_setscanlinecallback(void (*callback)(), int scanline)
+{
+	if (!callback)
+		slcallbackline = 400;
+	else
+		slcallbackline = scanline;
+	slcallback = callback;
+}
+
+void scanlinecallback_bizhawk()
+{
+	if (slcallback)
+		slcallback();
+}
diff --git a/libmeteor/source/debug.hpp b/libmeteor/source/debug.hpp
index c47e0813a3..64d0973709 100644
--- a/libmeteor/source/debug.hpp
+++ b/libmeteor/source/debug.hpp
@@ -32,6 +32,8 @@ void abort_bizhawk(const char *msg);
 void keyupdate_bizhawk();
 extern bool traceenabled;
 void trace_bizhawk(std::string msg);
+extern int slcallbackline;
+void scanlinecallback_bizhawk();
 
 #if 0
 #define met_abort(str) \
diff --git a/libmeteor/source/lcd.cpp b/libmeteor/source/lcd.cpp
index a8d045c80c..74c5b4c7ba 100644
--- a/libmeteor/source/lcd.cpp
+++ b/libmeteor/source/lcd.cpp
@@ -94,7 +94,8 @@ namespace AMeteor
 			else // no vcount match
 				dispstat &= ~(uint16_t)0x4;
 			// scanline callback for frontend
-			// ...
+			if (slcallbackline == vcount)
+				scanlinecallback_bizhawk();
 		}
 		else // if we were not H-Blanking
 		{