diff --git a/artiq/gateware/targets/sayma_amc_standalone.py b/artiq/gateware/targets/sayma_amc_standalone.py
index 73124afe7..5ef866d0a 100755
--- a/artiq/gateware/targets/sayma_amc_standalone.py
+++ b/artiq/gateware/targets/sayma_amc_standalone.py
@@ -160,7 +160,7 @@ class Standalone(MiniSoC, AMPSoC):
         self.csr_devices.append("rtm_fpga_cfg")
 
         # AMC/RTM serwb
-        serwb_pll = serwb.phy.SERWBPLL(125e6, 1.25e9, vco_div=2)
+        serwb_pll = serwb.phy.SERWBPLL(125e6, 625e6, vco_div=2)
         self.comb += serwb_pll.refclk.eq(self.crg.cd_sys.clk)
         self.submodules += serwb_pll
 
diff --git a/artiq/gateware/targets/sayma_rtm.py b/artiq/gateware/targets/sayma_rtm.py
index c438d469d..5861be3e8 100755
--- a/artiq/gateware/targets/sayma_rtm.py
+++ b/artiq/gateware/targets/sayma_rtm.py
@@ -140,7 +140,7 @@ class SaymaRTM(Module):
         self.comb += platform.request("hmc7043_reset").eq(0)
 
         # AMC/RTM serwb
-        serwb_pll = serwb.phy.SERWBPLL(125e6, 1.25e9, vco_div=1)
+        serwb_pll = serwb.phy.SERWBPLL(62.5e6, 625e6, vco_div=1)
         self.submodules += serwb_pll
 
         serwb_pads = platform.request("amc_rtm_serwb")