diff --git a/litedram/phy/a7ddrphy.py b/litedram/phy/a7ddrphy.py
index 017780d..6b581a0 100644
--- a/litedram/phy/a7ddrphy.py
+++ b/litedram/phy/a7ddrphy.py
@@ -1,3 +1,4 @@
+# 1:4 frequency-ratio DDR3 PHYs for Artix7
 # tCK=2.5ns CL=7 CWL=6
 
 from litex.gen import *
diff --git a/litedram/phy/k7ddrphy.py b/litedram/phy/k7ddrphy.py
index b6f1b57..fa1e2e3 100644
--- a/litedram/phy/k7ddrphy.py
+++ b/litedram/phy/k7ddrphy.py
@@ -1,3 +1,4 @@
+# 1:4 frequency-ratio DDR3 PHYs for Kintex7
 # tCK=5ns CL=7 CWL=6
 
 from litex.gen import *