diff --git a/artiq/firmware/libboard_artiq/hmc830_7043.rs b/artiq/firmware/libboard_artiq/hmc830_7043.rs
index 11dc77b2b..9a2aa5ac6 100644
--- a/artiq/firmware/libboard_artiq/hmc830_7043.rs
+++ b/artiq/firmware/libboard_artiq/hmc830_7043.rs
@@ -146,6 +146,7 @@ pub mod hmc7043 {
     const DAC_CLK_DIV: u32 = 2;
     const FPGA_CLK_DIV: u32 = 8;
     const SYSREF_DIV: u32 = 128;
+    const HMC_SYSREF_DIV: u32 = SYSREF_DIV*8; // Must be <= 4MHz
 
     // enabled, divider, analog phase shift, digital phase shift
     const OUTPUT_CONFIG: [(bool, u32, u8, u8); 14] = [
@@ -243,7 +244,6 @@ pub mod hmc7043 {
         spi_setup();
         info!("loading configuration...");
 
-        write(0x3, 0x10);  // Disable SYSREF timer
         write(0xA, 0x06);  // Disable the REFSYNCIN input
         write(0xB, 0x07);  // Enable the CLKIN input as LVPECL
         write(0x50, 0x1f); // Disable GPO pin
@@ -257,14 +257,17 @@ pub mod hmc7043 {
                    (1 << 4) |
                    (1 << 5));
 
+        write(0x5c, (HMC_SYSREF_DIV & 0xff) as u8);  // Set SYSREF timer divider
+        write(0x5d, ((HMC_SYSREF_DIV & 0x0f) >> 8) as u8);
+
         for channel in 0..14 {
             let channel_base = 0xc8 + 0x0a*(channel as u16);
             let (enabled, divider, aphase, dphase) = OUTPUT_CONFIG[channel];
 
             if enabled {
                 // Only clock channels need to be high-performance
-                if (channel % 2) == 0 { write(channel_base, 0x91); }
-                else { write(channel_base, 0x11); }
+                if (channel % 2) == 0 { write(channel_base, 0xd1); }
+                else { write(channel_base, 0x51); }
             }
             else { write(channel_base, 0x10); }
             write(channel_base + 0x1, (divider & 0x0ff) as u8);
@@ -279,7 +282,11 @@ pub mod hmc7043 {
             write(channel_base + 0x8, 0x08)
         }
 
+        write(0x1, 0x4a);  // Reset dividers and FSMs
+        write(0x1, 0x48);
+        write(0x1, 0xc8);  // Synchronize dividers
         write(0x1, 0x40);  // Unmute, high-performace/low-noise mode
+
         info!("  ...done");
 
         Ok(())