diff --git a/main.c b/main.c
index ac3d5c4..cfa16bf 100644
--- a/main.c
+++ b/main.c
@@ -222,6 +222,27 @@ int main()
   int command_read = voodoo2->fbiInit2 & 0xff;
   printf("dac read: DAC__RS__COMMAND: m: %02x\n", command_read);
 
+  /*
+    pixel clock: 40MHz
+    graphics/memory clock: 44.6MHz
+  */
+
+  int m = 54;
+  int n = 67;
+  dac_write_pll_16(voodoo2, DAC__PLL_PARAMETER__CLK0_f0_PLL, m, n);
+  mn_t clk0_f0_res = dac_read_pll_16(voodoo2, DAC__PLL_PARAMETER__CLK0_f0_PLL);
+  printf("dac read: DAC__PLL_PARAMETER__CLK0_f0_PLL: m: %02x n: %02x\n",
+         clk0_f0_res.m, clk0_f0_res.n);
+
+  int pll_control
+    = DAC__PLL_CONTROL__CLK0_SELECT(0) // f0
+    | DAC__PLL_CONTROL__CLK1_SELECT(0) // fA
+    | DAC__PLL_CONTROL__ENABLE_INTERNAL_CLOCK_SELECT;
+  dac_write_pll_8(voodoo2, DAC__PLL_PARAMETER__PLL_CONTROL, pll_control);
+  mn_t pll_control_res = dac_read_pll_16(voodoo2, DAC__PLL_PARAMETER__PLL_CONTROL);
+  printf("dac read: DAC__PLL_PARAMETER__PLL_CONTROL: m: %02x\n",
+         pll_control_res.m);
+
   ////////////////////////////////////////////////////////////////////////
   // cleanup
   ////////////////////////////////////////////////////////////////////////