diff --git a/soc/runtime/bridge.c b/soc/runtime/bridge.c
index 3c4097c39..8ae83c1cc 100644
--- a/soc/runtime/bridge.c
+++ b/soc/runtime/bridge.c
@@ -66,10 +66,6 @@ void bridge_main(void)
                 mailbox_acknowledge();
                 break;
             }
-            case MESSAGE_TYPE_BRG_DDS_INITALL:
-                dds_init_all();
-                mailbox_acknowledge();
-                break;
             case MESSAGE_TYPE_BRG_DDS_SEL: {
                 struct msg_brg_dds_sel *msg;
 
diff --git a/soc/runtime/bridge_ctl.c b/soc/runtime/bridge_ctl.c
index 14a042a0d..11182efb9 100644
--- a/soc/runtime/bridge_ctl.c
+++ b/soc/runtime/bridge_ctl.c
@@ -23,11 +23,6 @@ void brg_start(void)
     }
 }
 
-void brg_stop(void)
-{
-    kloader_stop();
-}
-
 void brg_ttloe(int n, int value)
 {
     struct msg_brg_ttl_out msg;
@@ -48,14 +43,6 @@ void brg_ttlo(int n, int value)
     mailbox_send_and_wait(&msg);
 }
 
-void brg_ddsinitall(void)
-{
-    struct msg_base msg;
-
-    msg.type = MESSAGE_TYPE_BRG_DDS_INITALL;
-    mailbox_send_and_wait(&msg);
-}
-
 void brg_ddssel(int channel)
 {
     struct msg_brg_dds_sel msg;
diff --git a/soc/runtime/bridge_ctl.h b/soc/runtime/bridge_ctl.h
index d87f83812..e6d2b7306 100644
--- a/soc/runtime/bridge_ctl.h
+++ b/soc/runtime/bridge_ctl.h
@@ -2,12 +2,10 @@
 #define __BRIDGE_CTL_H
 
 void brg_start(void);
-void brg_stop(void);
 
 void brg_ttloe(int n, int value);
 void brg_ttlo(int n, int value);
 
-void brg_ddsinitall(void);
 void brg_ddssel(int channel);
 void brg_ddsreset(void);
 unsigned int brg_ddsread(unsigned int address);
diff --git a/soc/runtime/clock.c b/soc/runtime/clock.c
index 171fb6f30..0d0d3f4c3 100644
--- a/soc/runtime/clock.c
+++ b/soc/runtime/clock.c
@@ -62,7 +62,7 @@ int watchdog_set(int ms)
             break;
         }
     if(id < 0) {
-        log("Failed to add watchdog");
+        log("WARNING: Failed to add watchdog");
         return id;
     }
 
diff --git a/soc/runtime/dds.c b/soc/runtime/dds.c
index f07684265..7d120a0cd 100644
--- a/soc/runtime/dds.c
+++ b/soc/runtime/dds.c
@@ -33,19 +33,6 @@
         now += DURATION_WRITE; \
     } while(0)
 
-void dds_init_all(void)
-{
-    int i;
-    long long int now;
-
-    now = rtio_get_counter() + 10000;
-    for(i=0;i<DDS_CHANNEL_COUNT;i++) {
-        dds_init(now, i);
-        now += DURATION_INIT + DURATION_WRITE; /* + FUD time */
-    }
-    while(rtio_get_counter() < now);
-}
-
 void dds_init(long long int timestamp, int channel)
 {
     long long int now;
diff --git a/soc/runtime/dds.h b/soc/runtime/dds.h
index 2e3a4d07e..2c2247b04 100644
--- a/soc/runtime/dds.h
+++ b/soc/runtime/dds.h
@@ -54,7 +54,6 @@ enum {
     PHASE_MODE_TRACKING = 2
 };
 
-void dds_init_all(void);
 void dds_init(long long int timestamp, int channel);
 void dds_batch_enter(long long int timestamp);
 void dds_batch_exit(void);
diff --git a/soc/runtime/kloader.c b/soc/runtime/kloader.c
index 0cdf56634..4fff4790a 100644
--- a/soc/runtime/kloader.c
+++ b/soc/runtime/kloader.c
@@ -2,6 +2,7 @@
 #include <generated/csr.h>
 
 #include "log.h"
+#include "clock.h"
 #include "flash_storage.h"
 #include "mailbox.h"
 #include "messages.h"
@@ -91,33 +92,50 @@ void kloader_start_user_kernel(kernel_function k)
     start_kernel_cpu((void *)k);
 }
 
-void kloader_start_idle_kernel(void)
+static int kloader_start_flash_kernel(char *key)
 {
     char buffer[32*1024];
-    int len;
+    unsigned int len, remain;
     kernel_function k;
 
     if(!kernel_cpu_reset_read()) {
-        log("BUG: attempted to start kernel CPU while already running (idle kernel)");
-        return;
+        log("BUG: attempted to start kernel CPU while already running (%s)", key);
+        return 0;
     }
 #if (defined CSR_SPIFLASH_BASE && defined SPIFLASH_PAGE_SIZE)
-    len = fs_read("idle_kernel", buffer, sizeof(buffer), NULL);
+    len = fs_read(key, buffer, sizeof(buffer), &remain);
     if(len <= 0)
-        return;
+        return 0;
+    if(remain) {
+        log("ERROR: %s too long", key);
+        return 0;
+    }
     if(!kloader_load(buffer, len)) {
-        log("Failed to load ELF binary for idle kernel");
-        return;
+        log("ERROR: failed to load ELF binary (%s)", key);
+        return 0;
     }
     k = kloader_find("run");
     if(!k) {
-        log("Failed to find entry point for ELF kernel");
-        return;
+        log("ERROR: failed to find entry point for ELF kernel (%s)", key);
+        return 0;
     }
     start_kernel_cpu((void *)k);
+    return 1;
+#else
+    return 0;
 #endif
 }
 
+int kloader_start_startup_kernel(void)
+{
+    return kloader_start_flash_kernel("startup_kernel");
+}
+
+int kloader_start_idle_kernel(void)
+{
+    return kloader_start_flash_kernel("idle_kernel");
+}
+
 void kloader_stop(void)
 {
     kernel_cpu_reset_write(1);
@@ -140,6 +158,8 @@ int kloader_is_essential_kmsg(int msgtype)
         case MESSAGE_TYPE_NOW_INIT_REQUEST:
         case MESSAGE_TYPE_NOW_SAVE:
         case MESSAGE_TYPE_LOG:
+        case MESSAGE_TYPE_WATCHDOG_SET_REQUEST:
+        case MESSAGE_TYPE_WATCHDOG_CLEAR:
             return 1;
         default:
             return 0;
@@ -179,6 +199,22 @@ void kloader_service_essential_kmsg(void)
                 mailbox_acknowledge();
                 break;
             }
+            case MESSAGE_TYPE_WATCHDOG_SET_REQUEST: {
+                struct msg_watchdog_set_request *msg = (struct msg_watchdog_set_request *)umsg;
+                struct msg_watchdog_set_reply reply;
+
+                reply.type = MESSAGE_TYPE_WATCHDOG_SET_REPLY;
+                reply.id = watchdog_set(msg->ms);
+                mailbox_send_and_wait(&reply);
+                break;
+            }
+            case MESSAGE_TYPE_WATCHDOG_CLEAR: {
+                struct msg_watchdog_clear *msg = (struct msg_watchdog_clear *)umsg;
+
+                watchdog_clear(msg->id);
+                mailbox_acknowledge();
+                break;
+            }
             default:
                 /* handled elsewhere */
                 break;
diff --git a/soc/runtime/kloader.h b/soc/runtime/kloader.h
index ceefbc89d..8f6091d28 100644
--- a/soc/runtime/kloader.h
+++ b/soc/runtime/kloader.h
@@ -12,7 +12,8 @@ int kloader_load(void *buffer, int length);
 kernel_function kloader_find(const char *name);
 
 void kloader_start_bridge(void);
-void kloader_start_idle_kernel(void);
+int kloader_start_startup_kernel(void);
+int kloader_start_idle_kernel(void);
 void kloader_start_user_kernel(kernel_function k);
 void kloader_stop(void);
 
diff --git a/soc/runtime/main.c b/soc/runtime/main.c
index bdd9d4b8c..f020b74ea 100644
--- a/soc/runtime/main.c
+++ b/soc/runtime/main.c
@@ -30,13 +30,6 @@
 #include "session.h"
 #include "moninj.h"
 
-static void common_init(void)
-{
-    brg_start();
-    brg_ddsinitall();
-    kloader_stop();
-}
-
 #ifdef CSR_ETHMAC_BASE
 
 u32_t sys_now(void)
@@ -260,7 +253,7 @@ int main(void)
         test_main();
     } else {
         puts("Entering regular mode.");
-        common_init();
+        session_startup_kernel();
         regular_main();
     }
     return 0;
diff --git a/soc/runtime/messages.h b/soc/runtime/messages.h
index 221b394a3..4a4e10737 100644
--- a/soc/runtime/messages.h
+++ b/soc/runtime/messages.h
@@ -19,7 +19,6 @@ enum {
     MESSAGE_TYPE_BRG_READY,
     MESSAGE_TYPE_BRG_TTL_O,
     MESSAGE_TYPE_BRG_TTL_OE,
-    MESSAGE_TYPE_BRG_DDS_INITALL,
     MESSAGE_TYPE_BRG_DDS_SEL,
     MESSAGE_TYPE_BRG_DDS_RESET,
     MESSAGE_TYPE_BRG_DDS_READ_REQUEST,
diff --git a/soc/runtime/rtiocrg.c b/soc/runtime/rtiocrg.c
index 255f2a308..de56fde0d 100644
--- a/soc/runtime/rtiocrg.c
+++ b/soc/runtime/rtiocrg.c
@@ -1,6 +1,6 @@
-#include <stdio.h>
 #include <generated/csr.h>
 
+#include "log.h"
 #include "clock.h"
 #include "flash_storage.h"
 #include "rtiocrg.h"
@@ -17,17 +17,17 @@ void rtiocrg_init(void)
     clk = 0;
     fs_read("startup_clock", &b, 1, NULL);
     if(b == 'i')
-        printf("Startup RTIO clock: internal\n");
+        log("Startup RTIO clock: internal");
     else if(b == 'e') {
-        printf("Startup RTIO clock: external\n");
+        log("Startup RTIO clock: external");
         clk = 1;
     } else
-        printf("WARNING: unknown startup_clock entry in flash storage\n");
+        log("ERROR: unrecognized startup_clock entry in flash storage");
 
     if(!rtiocrg_switch_clock(clk)) {
-        printf("WARNING: startup RTIO clock failed\n");
-        printf("WARNING: this may cause the system initialization to fail\n");
-        printf("WARNING: fix clocking and reset the device\n");
+        log("ERROR: startup RTIO clock failed");
+        log("WARNING: this may cause the system initialization to fail");
+        log("WARNING: fix clocking and reset the device");
     }
 }
 
diff --git a/soc/runtime/session.c b/soc/runtime/session.c
index c0908639c..a76a51687 100644
--- a/soc/runtime/session.c
+++ b/soc/runtime/session.c
@@ -64,6 +64,44 @@ enum {
     USER_KERNEL_WAIT_RPC /* < must come after _RUNNING */
 };
 
+void session_startup_kernel(void)
+{
+    struct msg_base *umsg;
+
+    now = -1;
+    watchdog_init();
+    if(!kloader_start_startup_kernel())
+        return;
+
+    while(1) {
+        kloader_service_essential_kmsg();
+
+        umsg = mailbox_receive();
+        if(umsg) {
+            if(!kloader_validate_kpointer(umsg))
+                break;
+            if(kloader_is_essential_kmsg(umsg->type))
+                continue;
+            if(umsg->type == MESSAGE_TYPE_FINISHED)
+                break;
+            else if(umsg->type == MESSAGE_TYPE_EXCEPTION) {
+                log("WARNING: startup kernel ended with exception");
+                break;
+            } else {
+                log("ERROR: received invalid message type from kernel CPU");
+                break;
+            }
+        }
+
+        if(watchdog_expired()) {
+            log("WARNING: watchdog expired in startup kernel");
+            break;
+        }
+    }
+    kloader_stop();
+    log("Startup kernel terminated");
+}
+
 void session_start(void)
 {
     buffer_in_index = 0;
@@ -77,6 +115,7 @@ void session_end(void)
 {
     kloader_stop();
     now = -1;
+    watchdog_init();
     kloader_start_idle_kernel();
 }
 
@@ -490,22 +529,6 @@ static int process_kmsg(struct msg_base *umsg)
             mailbox_acknowledge();
             break;
         }
-        case MESSAGE_TYPE_WATCHDOG_SET_REQUEST: {
-            struct msg_watchdog_set_request *msg = (struct msg_watchdog_set_request *)umsg;
-            struct msg_watchdog_set_reply reply;
-
-            reply.type = MESSAGE_TYPE_WATCHDOG_SET_REPLY;
-            reply.id = watchdog_set(msg->ms);
-            mailbox_send_and_wait(&reply);
-            break;
-        }
-        case MESSAGE_TYPE_WATCHDOG_CLEAR: {
-            struct msg_watchdog_clear *msg = (struct msg_watchdog_clear *)umsg;
-
-            watchdog_clear(msg->id);
-            mailbox_acknowledge();
-            break;
-        }
         case MESSAGE_TYPE_RPC_REQUEST: {
             struct msg_rpc_request *msg = (struct msg_rpc_request *)umsg;
 
@@ -516,7 +539,7 @@ static int process_kmsg(struct msg_base *umsg)
             break;
         }
         default: {
-            log("Received invalid message type from kernel CPU");
+            log("ERROR: received invalid message type from kernel CPU");
             return 0;
         }
     }
diff --git a/soc/runtime/session.h b/soc/runtime/session.h
index 988d0f6b0..5728103ae 100644
--- a/soc/runtime/session.h
+++ b/soc/runtime/session.h
@@ -1,6 +1,7 @@
 #ifndef __SESSION_H
 #define __SESSION_H
 
+void session_startup_kernel(void);
 void session_start(void);
 void session_end(void);