diff --git a/README.md b/README.md
index b39e8b9..a172a71 100644
--- a/README.md
+++ b/README.md
@@ -65,6 +65,7 @@ section (thicker power lines, separately routed feedback)
     [x] Silkscreen JTAG signal names on 6-pin 2.54 mm header
     [x] Silkscreen remove OLED outline
     [x] Solder stop mask must go inbetween all SMD chip pads
+    [ ] External differential clock input
     [ ] Thinner copper, more spacing to SDRAM-FPGA
     [ ] physically sprinkle VCC blocator capacitors under BGA
     [ ] Values on silkscreen