diff --git a/artiq/firmware/runtime/main.rs b/artiq/firmware/runtime/main.rs
index cfd420e04..a0af6667f 100644
--- a/artiq/firmware/runtime/main.rs
+++ b/artiq/firmware/runtime/main.rs
@@ -131,7 +131,7 @@ fn startup() {
 fn setup_si5324_as_synthesizer()
 {
     // 125MHz output, from 100MHz CLKIN2 reference, 586 Hz
-    #[cfg(all(rtio_frequency = "125.0", si5324_ext_ref))]
+    #[cfg(all(not(si5324_sayma_ref), rtio_frequency = "125.0", si5324_ext_ref))]
     const SI5324_SETTINGS: board_artiq::si5324::FrequencySettings
         = board_artiq::si5324::FrequencySettings {
         n1_hs  : 10,
@@ -144,7 +144,7 @@ fn setup_si5324_as_synthesizer()
         crystal_ref: false
     };
     // 125MHz output, from crystal, 7 Hz
-    #[cfg(all(rtio_frequency = "125.0", not(si5324_ext_ref)))]
+    #[cfg(all(not(si5324_sayma_ref), rtio_frequency = "125.0", not(si5324_ext_ref)))]
     const SI5324_SETTINGS: board_artiq::si5324::FrequencySettings
         = board_artiq::si5324::FrequencySettings {
         n1_hs  : 10,
@@ -157,7 +157,7 @@ fn setup_si5324_as_synthesizer()
         crystal_ref: true
     };
     // 150MHz output, from crystal
-    #[cfg(all(rtio_frequency = "150.0", not(si5324_ext_ref)))]
+    #[cfg(all(not(si5324_sayma_ref), rtio_frequency = "150.0", not(si5324_ext_ref)))]
     const SI5324_SETTINGS: board_artiq::si5324::FrequencySettings
         = board_artiq::si5324::FrequencySettings {
         n1_hs  : 9,
@@ -169,6 +169,19 @@ fn setup_si5324_as_synthesizer()
         bwsel  : 3,
         crystal_ref: true
     };
+    // 100MHz output, from crystal (reference for HMC830)
+    #[cfg(si5324_sayma_ref)]
+    const SI5324_SETTINGS: board_artiq::si5324::FrequencySettings
+        = board_artiq::si5324::FrequencySettings {
+        n1_hs  : 9,
+        nc1_ls : 6,
+        n2_hs  : 10,
+        n2_ls  : 33732,
+        n31    : 9370,
+        n32    : 7139,
+        bwsel  : 3,
+        crystal_ref: true
+    };
     board_artiq::si5324::setup(&SI5324_SETTINGS,
         board_artiq::si5324::Input::Ckin2).expect("cannot initialize Si5324");
 }
diff --git a/artiq/gateware/targets/sayma_amc.py b/artiq/gateware/targets/sayma_amc.py
index 165d09c50..abb614977 100755
--- a/artiq/gateware/targets/sayma_amc.py
+++ b/artiq/gateware/targets/sayma_amc.py
@@ -139,6 +139,16 @@ class Standalone(MiniSoC, AMPSoC, RTMCommon):
 
         platform = self.platform
 
+        self.submodules.si5324_rst_n = gpio.GPIOOut(platform.request("si5324").rst_n)
+        self.csr_devices.append("si5324_rst_n")
+        i2c = self.platform.request("i2c")
+        self.submodules.i2c = gpio.GPIOTristate([i2c.scl, i2c.sda])
+        self.csr_devices.append("i2c")
+        self.config["I2C_BUS_COUNT"] = 1
+        self.config["HAS_SI5324"] = None
+        self.config["SI5324_AS_SYNTHESIZER"] = None
+        self.config["SI5324_SAYMA_REF"] = None
+
         # RTIO
         rtio_channels = []
         for i in range(4):
@@ -233,6 +243,16 @@ class Master(MiniSoC, AMPSoC, RTMCommon):
         platform = self.platform
         rtio_clk_freq = 150e6
 
+        self.submodules.si5324_rst_n = gpio.GPIOOut(platform.request("si5324").rst_n)
+        self.csr_devices.append("si5324_rst_n")
+        i2c = self.platform.request("i2c")
+        self.submodules.i2c = gpio.GPIOTristate([i2c.scl, i2c.sda])
+        self.csr_devices.append("i2c")
+        self.config["I2C_BUS_COUNT"] = 1
+        self.config["HAS_SI5324"] = None
+        self.config["SI5324_AS_SYNTHESIZER"] = None
+        self.config["SI5324_SAYMA_REF"] = None
+
         self.comb += [
             platform.request("sfp_tx_disable", i).eq(0)
             for i in range(2)