diff --git a/artiq/gateware/targets/sayma_amc.py b/artiq/gateware/targets/sayma_amc.py
index d0bd99450..165d09c50 100755
--- a/artiq/gateware/targets/sayma_amc.py
+++ b/artiq/gateware/targets/sayma_amc.py
@@ -228,7 +228,7 @@ class Master(MiniSoC, AMPSoC, RTMCommon):
                          **kwargs)
         AMPSoC.__init__(self)
         RTMCommon.__init__(self)
-        self.config["HMC830_REF"] = "150"
+        self.config["HMC830_REF"] = "100"
 
         platform = self.platform
         rtio_clk_freq = 150e6