diff --git a/cores/archie/fpga/mist/archimedes_mist_top.v b/cores/archie/fpga/mist/archimedes_mist_top.v
index e9e0e6e..806d505 100644
--- a/cores/archie/fpga/mist/archimedes_mist_top.v
+++ b/cores/archie/fpga/mist/archimedes_mist_top.v
@@ -97,6 +97,7 @@ wire [7:0] joyA;
 wire [7:0] joyB;
 wire [1:0] buttons;
 wire [1:0] switches;
+wire       scandoubler_disable;
 wire       ypbpr;
 
 // the top file should generate the correct clocks for the machine
@@ -147,8 +148,8 @@ assign VGA_R = ypbpr?Pr:osd_r_o;
 assign VGA_G = ypbpr? Y:osd_g_o;
 assign VGA_B = ypbpr?Pb:osd_b_o;
 wire   CSync = ~(core_hs ^ core_vs);
-assign VGA_HS = ypbpr ? CSync : core_hs;
-assign VGA_VS = ypbpr? 1'b1 : core_vs;
+assign VGA_HS = (scandoubler_disable | ypbpr) ? CSync : core_hs;
+assign VGA_VS = (scandoubler_disable | ypbpr) ? 1'b1 : core_vs;
 
 // de-multiplex spi outputs from user_io and data_io
 assign SPI_DO = (CONF_DATA0==0)?user_io_sdo:(SPI_SS2==0)?data_io_sdo:1'bZ;
@@ -162,12 +163,13 @@ user_io user_io(
    .SPI_MISO      (user_io_sdo           ),   // tristate handling inside user_io
    .SPI_MOSI      (SPI_DI           ),
 
-   .SWITCHES      (switches         ),
-   .BUTTONS       (buttons          ),
-   .ypbpr         (ypbpr            ),
+	.SWITCHES      (switches         ),
+	.BUTTONS       (buttons          ),
+	.scandoubler_disable(scandoubler_disable),
+	.ypbpr         (ypbpr            ),
 
-   .JOY0          (joyA             ),
-   .JOY1          (joyB             ),
+	.JOY0          (joyA             ),
+	.JOY1          (joyB             ),
 
 	.kbd_out_data   ( kbd_out_data   ),
 	.kbd_out_strobe ( kbd_out_strobe ),
diff --git a/cores/archie/fpga/mist/user_io.v b/cores/archie/fpga/mist/user_io.v
index c6c8e21..9509701 100644
--- a/cores/archie/fpga/mist/user_io.v
+++ b/cores/archie/fpga/mist/user_io.v
@@ -31,6 +31,7 @@ module user_io (
 
         output     [7:0] JOY0,
         output     [7:0] JOY1,
+        output           scandoubler_disable,
         output           ypbpr,
 
         input      [7:0] kbd_out_data,
@@ -60,7 +61,9 @@ assign JOY1 = joystick_1[7:0];
 
 assign BUTTONS  = but_sw[1:0];
 assign SWITCHES = but_sw[3:2];
+assign scandoubler_disable = but_sw[4];
 assign ypbpr = but_sw[5];
+
 // this variant of user_io is for the achie core (type == a6) only
 wire [7:0] core_type = 8'ha6;
 reg  [7:0] spi_byte_out;