diff --git a/src/main.c b/src/main.c
index 47c84a8..a8a2bdf 100644
--- a/src/main.c
+++ b/src/main.c
@@ -122,8 +122,8 @@ int main()
 	vga_hsync_program_init(pio, sm1, offset1);
 	printf("Feeding horizontal sync...\n");
 	// low pulse is X pixels long, and SM runs at 4x of pixel clock
-	pio_sm_put_blocking(pio, sm1, 63 * 4);
-	pio_sm_put_blocking(pio, sm1, 775 * 4);
+	pio_sm_put_blocking(pio, sm1, 64 * 4);
+	pio_sm_put_blocking(pio, sm1, 765 * 4);
 
 	// VGA VSYNC program
 	uint offset2 = pio_add_program(pio, &vga_vsync_program);
@@ -131,8 +131,9 @@ int main()
 	printf("Starting VGA vsync machine on %u...\n", sm2);
 	vga_vsync_program_init(pio, sm2, offset2);
 	printf("Feeding vertical sync...\n");
-	pio_sm_put_blocking(pio, sm2, 2520 * 4);
-	pio_sm_put_blocking(pio, sm2, 420000 * 4);
+	// low pulse assert lasts for 3 horizontal lines, then adjust by one
+	pio_sm_put_blocking(pio, sm2, 3 - 1);
+	pio_sm_put_blocking(pio, sm2, 500 - 3 - 1);
 
 	printf("Start!\n");
 
diff --git a/src/vga.pio b/src/vga.pio
index f3b9b42..bc6b580 100644
--- a/src/vga.pio
+++ b/src/vga.pio
@@ -13,9 +13,10 @@ entrypoint_vga_hsync:
     mov isr, osr
     pull
 
-loope:
-    set y, 15
 loop:
+    nop
+    irq set 0
+
     mov x, isr
     set pins, 0
 hsync_pulse:
@@ -25,10 +26,9 @@ hsync_pulse:
     set pins, 1
 hsync_idle:
     jmp x-- hsync_idle
-    jmp y-- loop
+    nop
+    jmp loop
 
-    irq set 0
-    jmp loope
 
 .program vga_vsync
 
@@ -38,11 +38,17 @@ entrypoint_vga_vsync:
     pull
 
 loop:
-    wait irq 0
+
     mov x, isr
-    set pins, 0
 vsync_pulse:
+    wait irq 0
+    set pins, 0
     jmp x-- vsync_pulse
 
+    mov x, osr
+vsync_idle:
+    wait irq 0
     set pins, 1
+    jmp x-- vsync_idle
+
     jmp loop