diff --git a/arch/aarch64/kernel/timer.c b/arch/aarch64/kernel/timer.c
index ed86c1691..62716f402 100644
--- a/arch/aarch64/kernel/timer.c
+++ b/arch/aarch64/kernel/timer.c
@@ -50,7 +50,7 @@ extern int32_t boot_processor;
 
 #ifdef DYNAMIC_TICKS
 DEFINE_PER_CORE(uint64_t, last_tsc, 0);
-static uint64_t boot_tsc = 0;
+static uint64_t boot_tsc __attribute__ ((section(".data"))) = 0;
 
 void check_ticks(void)
 {
@@ -59,7 +59,7 @@ void check_ticks(void)
 		return;
 
 	const uint64_t curr_tsc = get_cntpct();
-	rmb();
+	mb();
 
 	const uint64_t diff_tsc = curr_tsc - per_core(last_tsc);
 	const uint64_t diff_ticks = (diff_tsc * (uint64_t) TIMER_FREQ) / freq_hz;
@@ -70,7 +70,22 @@ void check_ticks(void)
 		rmb();
 	}
 }
+
+uint64_t get_uptime(void)
+{
+	const uint64_t curr_tsc = get_cntpct();
+
+	mb();
+	uint64_t diff = curr_tsc - per_core(last_rdtsc);
+
+	return (1000ULL*diff) / freq_hz;
+}
 #else
+uint64_t get_uptime(void)
+{
+	return (get_clock_tick() * 1000) / TIMER_FREQ;
+}
+
 static void restart_periodic_timer(void)
 {
 	set_cntp_tval(freq_hz / TIMER_FREQ);
@@ -172,13 +187,19 @@ int timer_wait(unsigned int ticks)
 	return 0;
 }
 
+int clock_init(void)
+{
+#ifdef DYNAMIC_TICKS
+	if (!boot_tsc)
+		boot_tsc = get_cntpct();
+#endif
+
+	return 0;
+}
+
 int timer_init(void)
 {
 #ifdef DYNAMIC_TICKS
-	if (boot_tsc)
-		return 0;
-
-	boot_tsc = get_cntpct();
 	set_per_core(last_tsc, boot_tsc);
 #endif
 
diff --git a/arch/x86_64/kernel/timer.c b/arch/x86_64/kernel/timer.c
index 58172bb72..6fe5412b9 100644
--- a/arch/x86_64/kernel/timer.c
+++ b/arch/x86_64/kernel/timer.c
@@ -47,7 +47,7 @@ extern int32_t boot_processor;
 
 #ifdef DYNAMIC_TICKS
 DEFINE_PER_CORE(uint64_t, last_rdtsc, 0);
-uint64_t boot_tsc = 0;
+uint64_t boot_tsc __attribute__ ((section(".data"))) = 0;
 
 void check_ticks(void)
 {
@@ -56,7 +56,7 @@ void check_ticks(void)
 		return;
 
 	const uint64_t curr_rdtsc = rdtsc();
-	rmb();
+	mb();
 
 	const uint64_t diff_cycles = curr_rdtsc - per_core(last_rdtsc);
 	const uint64_t cpu_freq_hz = 1000000ULL * (uint64_t) get_cpu_frequency();
@@ -68,6 +68,22 @@ void check_ticks(void)
 		mb();
 	}
 }
+
+uint64_t get_uptime(void)
+{
+	const uint64_t cpu_freq_hz = 1000000ULL * (uint64_t) get_cpu_frequency();
+	const uint64_t curr_tsc = rdtsc();
+
+	mb();
+	uint64_t diff = curr_tsc - per_core(last_rdtsc);
+
+	return (1000ULL*diff) / cpu_freq_hz;
+}
+#else
+uint64_t get_uptime(void)
+{
+	return (get_clock_tick() * 1000) / TIMER_FREQ;
+}
 #endif
 
 /*
@@ -162,6 +178,16 @@ static int pit_init(void)
 	return 0;
 }
 
+int clock_init(void)
+{
+#ifdef DYNAMIC_TICKS
+	if (!boot_tsc)
+		boot_tsc = has_rdtscp() ? rdtscp(NULL) : rdtsc();
+#endif
+
+	return 0;
+}
+
 /*
  * Sets up the system clock by installing the timer handler
  * into IRQ0
@@ -169,11 +195,7 @@ static int pit_init(void)
 int timer_init(void)
 {
 #ifdef DYNAMIC_TICKS
-	if (boot_tsc)
-	{
-		set_per_core(last_rdtsc, boot_tsc);
-		return 0;
-	}
+	set_per_core(last_rdtsc, boot_tsc);
 #endif
 
 	/*
@@ -183,11 +205,6 @@ int timer_init(void)
 	irq_install_handler(32, timer_handler);
 	irq_install_handler(123, timer_handler);
 
-#ifdef DYNAMIC_TICKS
-	boot_tsc = has_rdtscp() ? rdtscp(NULL) : rdtsc();
-	set_per_core(last_rdtsc, boot_tsc);
-#endif
-
 	if (cpu_freq) // do we need to configure the timer?
 		return 0;
 
diff --git a/include/hermit/time.h b/include/hermit/time.h
index 5c32cd5fe..a1e2a628f 100644
--- a/include/hermit/time.h
+++ b/include/hermit/time.h
@@ -55,6 +55,9 @@ struct tms {
  */
 int timer_init(void);
 
+/** @brief Initialize clock */
+int clock_init(void);
+
 /** @brief Initialized a timer
  *
  * @param ticks Amount of ticks to wait
@@ -81,9 +84,8 @@ static inline uint64_t get_clock_tick(void)
  */
 static inline void sleep(unsigned int sec) { timer_wait(sec*TIMER_FREQ); }
 
-/** @brief Get milliseconds since system boot
- */
-static inline uint64_t get_uptime() { return (get_clock_tick() * 1000) / TIMER_FREQ; }
+/** @brief Get milliseconds since system boot */
+uint64_t get_uptime(void);
 
 #ifdef __cplusplus
 }
diff --git a/kernel/main.c b/kernel/main.c
index 9da479e85..72681ff93 100644
--- a/kernel/main.c
+++ b/kernel/main.c
@@ -113,14 +113,15 @@ extern void signal_init();
 
 static int hermit_init(void)
 {
-	uint32_t i;
+	clock_init();
+
 	size_t sz = (size_t) &percore_end0 - (size_t) &percore_start;
 
 	// initialize .kbss sections
 	memset((void*)&tdata_end, 0x00, (size_t) &__bss_start - (size_t) &tdata_end);
 
 	// initialize .percore section => copy first section to all other sections
-	for(i=1; i<MAX_CORES; i++)
+	for(uint32_t i=1; i<MAX_CORES; i++)
 		memcpy((char*) &percore_start + i*sz, (char*) &percore_start, sz);
 
 	koutput_init();
@@ -391,7 +392,7 @@ static int initd(void* arg)
 		uhyve_send(UHYVE_PORT_CMDVAL,
 				(unsigned)virt_to_phys((size_t)&uhyve_cmdval_phys));
 
-		LOG_INFO("Boot time: %d ms\n", (get_clock_tick() * 1000) / TIMER_FREQ);
+		LOG_INFO("Boot time: %d ms\n", get_uptime());
 		libc_start(uhyve_cmdsize.argc, uhyve_cmdval.argv, uhyve_cmdval.envp);
 
 		for(i=0; i<uhyve_cmdsize.argc; i++)