diff --git a/artiq/firmware/runtime/rtio_clocking.rs b/artiq/firmware/runtime/rtio_clocking.rs
index 1123b3d1a..f094e5383 100644
--- a/artiq/firmware/runtime/rtio_clocking.rs
+++ b/artiq/firmware/runtime/rtio_clocking.rs
@@ -1,5 +1,4 @@
 use board_misoc::config;
-#[cfg(si5324_as_synthesizer)]
 use board_artiq::si5324;
 use board_misoc::{csr, clock};
 
@@ -86,15 +85,14 @@ pub mod crg {
 
 // Si5324 input to select for locking to an external clock (as opposed to
 // a recovered link clock in DRTIO satellites, which is handled elsewhere).
-#[cfg(all(si5324_as_synthesizer, soc_platform = "kasli", hw_rev = "v2.0"))]
+#[cfg(all(soc_platform = "kasli", hw_rev = "v2.0"))]
 const SI5324_EXT_INPUT: si5324::Input = si5324::Input::Ckin1;
-#[cfg(all(si5324_as_synthesizer, soc_platform = "kasli", not(hw_rev = "v2.0")))]
+#[cfg(all(soc_platform = "kasli", not(hw_rev = "v2.0")))]
 const SI5324_EXT_INPUT: si5324::Input = si5324::Input::Ckin2;
-#[cfg(all(si5324_as_synthesizer, soc_platform = "kc705"))]
+#[cfg(all(soc_platform = "kc705"))]
 const SI5324_EXT_INPUT: si5324::Input = si5324::Input::Ckin2;
 
-#[cfg(si5324_as_synthesizer)]
-fn setup_si5324_as_synthesizer(cfg: RtioClock) {
+fn setup_si5324_pll(cfg: RtioClock) {
     let (si5324_settings, si5324_ref_input) = match cfg {
         RtioClock::Ext0_Synth0_10to125 => { // 125 MHz output from 10 MHz CLKINx reference, 504 Hz BW
             info!("using 10MHz reference to make 125MHz RTIO clock with PLL");
@@ -209,7 +207,7 @@ fn setup_si5324(clock_cfg: RtioClock) {
             info!("using external RTIO clock with PLL bypass");
             si5324::bypass(SI5324_EXT_INPUT).expect("cannot bypass Si5324")
         },
-        _ => setup_si5324_as_synthesizer(clock_cfg),
+        _ => setup_si5324_pll(clock_cfg),
     }
 
     // switch sysclk source to si5324
diff --git a/artiq/gateware/targets/kasli.py b/artiq/gateware/targets/kasli.py
index 1d33c6e2a..f26e839dd 100755
--- a/artiq/gateware/targets/kasli.py
+++ b/artiq/gateware/targets/kasli.py
@@ -136,7 +136,6 @@ class Tester(StandaloneBase):
             dds = "ad9910"
         StandaloneBase.__init__(self, hw_rev=hw_rev, **kwargs)
 
-        self.config["SI5324_AS_SYNTHESIZER"] = None
         # self.config["SI5324_EXT_REF"] = None
         self.config["RTIO_FREQUENCY"] = "125.0"
         if hw_rev == "v1.0":
@@ -174,7 +173,6 @@ class SUServo(StandaloneBase):
             hw_rev = "v2.0"
         StandaloneBase.__init__(self, hw_rev=hw_rev, **kwargs)
 
-        self.config["SI5324_AS_SYNTHESIZER"] = None
         # self.config["SI5324_EXT_REF"] = None
         self.config["RTIO_FREQUENCY"] = "125.0"
         if hw_rev == "v1.0":
@@ -254,7 +252,6 @@ class MasterBase(MiniSoC, AMPSoC):
         self.config["I2C_BUS_COUNT"] = 1
         self.config["HAS_SI5324"] = None
         self.config["SI5324_SOFT_RESET"] = None
-        self.config["SI5324_AS_SYNTHESIZER"] = None
         self.config["RTIO_FREQUENCY"] = str(rtio_clk_freq/1e6)
 
         drtio_data_pads = []
diff --git a/artiq/gateware/targets/kasli_generic.py b/artiq/gateware/targets/kasli_generic.py
index a356aaba1..910ff46ca 100755
--- a/artiq/gateware/targets/kasli_generic.py
+++ b/artiq/gateware/targets/kasli_generic.py
@@ -23,7 +23,6 @@ class GenericStandalone(StandaloneBase):
         self.class_name_override = description["variant"]
         StandaloneBase.__init__(self, hw_rev=hw_rev, **kwargs)
 
-        self.config["SI5324_AS_SYNTHESIZER"] = None
         self.config["RTIO_FREQUENCY"] = "{:.1f}".format(description["rtio_frequency"]/1e6)
         if "ext_ref_frequency" in description:
             self.config["SI5324_EXT_REF"] = None
diff --git a/artiq/gateware/targets/kc705.py b/artiq/gateware/targets/kc705.py
index 4aac6e2ce..d80af96be 100755
--- a/artiq/gateware/targets/kc705.py
+++ b/artiq/gateware/targets/kc705.py
@@ -112,7 +112,6 @@ class _StandaloneBase(MiniSoC, AMPSoC):
         cdr_clk_buf = Signal()
 
         self.config["HAS_SI5324"] = None
-        self.config["SI5324_AS_SYNTHESIZER"] = None
         self.submodules.si5324_rst_n = gpio.GPIOOut(self.platform.request("si5324_33").rst_n)
         self.csr_devices.append("si5324_rst_n")
         self.specials += [
@@ -262,7 +261,6 @@ class _MasterBase(MiniSoC, AMPSoC):
         self.csr_devices.append("i2c")
         self.config["I2C_BUS_COUNT"] = 1
         self.config["HAS_SI5324"] = None
-        self.config["SI5324_AS_SYNTHESIZER"] = None
 
         rtio_clk_period = 1e9/self.drtio_transceiver.rtio_clk_freq
         # Constrain TX & RX timing for the first transceiver channel