diff --git a/techlibs/greenpak4/cells_sim.v b/techlibs/greenpak4/cells_sim.v
index f013d9b71..d3a176b88 100644
--- a/techlibs/greenpak4/cells_sim.v
+++ b/techlibs/greenpak4/cells_sim.v
@@ -75,6 +75,9 @@ module GP_LFOSC(input PWRDN, output reg CLKOUT);
 	
 	initial CLKOUT = 0;
 	
+	//auto powerdown not implemented for simulation
+	//output dividers not implemented for simulation
+	
 	always begin
 		if(PWRDN)
 			clkout = 0;
@@ -87,6 +90,29 @@ module GP_LFOSC(input PWRDN, output reg CLKOUT);
 	
 endmodule
 
+module GP_RINGOSC(input PWRDN, output reg CLKOUT);
+	
+	parameter PWRDN_EN = 0;
+	parameter AUTO_PWRDN = 0;
+	parameter OUT_DIV = 1;
+	
+	initial CLKOUT = 0;
+	
+	//output dividers not implemented for simulation
+	//auto powerdown not implemented for simulation
+	
+	always begin
+		if(PWRDN)
+			clkout = 0;
+		else begin
+			//half period of 27 MHz
+			#18.518;
+			clkout = ~clkout;
+		end
+	end
+	
+endmodule
+
 module GP_COUNT8(input CLK, input wire RST, output reg OUT);
 
 	parameter RESET_MODE 	= "RISING";