diff --git a/sys/kern/kern_cpu.c b/sys/kern/kern_cpu.c
index 7b0b58891b32..9f7f6156704d 100644
--- a/sys/kern/kern_cpu.c
+++ b/sys/kern/kern_cpu.c
@@ -158,12 +158,16 @@ cpufreq_attach(device_t dev)
 	CF_MTX_INIT(&sc->lock);
 	sc->curr_level.total_set.freq = CPUFREQ_VAL_UNKNOWN;
 	SLIST_INIT(&sc->saved_freq);
-	/* Try to get current CPU freq to use it as maximum later if needed */
-	pc = cpu_get_pcpu(dev);
-	if (cpu_est_clockrate(pc->pc_cpuid, &rate) == 0)
-		sc->max_mhz = rate / 1000000;
-	else
-		sc->max_mhz = CPUFREQ_VAL_UNKNOWN;
+	/* Try to get nominal CPU freq to use it as maximum later if needed */
+	sc->max_mhz = cpu_get_nominal_mhz(dev);
+	/* If that fails, try to measure the current rate */
+	if (sc->max_mhz <= 0) {
+		pc = cpu_get_pcpu(dev);
+		if (cpu_est_clockrate(pc->pc_cpuid, &rate) == 0)
+			sc->max_mhz = rate / 1000000;
+		else
+			sc->max_mhz = CPUFREQ_VAL_UNKNOWN;
+	}
 
 	/*
 	 * Only initialize one set of sysctls for all CPUs.  In the future,
@@ -581,15 +585,20 @@ cf_levels_method(device_t dev, struct cf_level *levels, int *count)
 	/*
 	 * If there are no absolute levels, create a fake one at 100%.  We
 	 * then cache the clockrate for later use as our base frequency.
-	 *
-	 * XXX This assumes that the first time through, if we only have
-	 * relative drivers, the CPU is currently running at 100%.
 	 */
 	if (TAILQ_EMPTY(&sc->all_levels)) {
 		if (sc->max_mhz == CPUFREQ_VAL_UNKNOWN) {
-			pc = cpu_get_pcpu(dev);
-			cpu_est_clockrate(pc->pc_cpuid, &rate);
-			sc->max_mhz = rate / 1000000;
+			sc->max_mhz = cpu_get_nominal_mhz(dev);
+			/*
+			 * If the CPU can't report a rate for 100%, hope
+			 * the CPU is running at its nominal rate right now,
+			 * and use that instead.
+			 */
+			if (sc->max_mhz <= 0) {
+				pc = cpu_get_pcpu(dev);
+				cpu_est_clockrate(pc->pc_cpuid, &rate);
+				sc->max_mhz = rate / 1000000;
+			}
 		}
 		memset(&sets[0], CPUFREQ_VAL_UNKNOWN, sizeof(*sets));
 		sets[0].freq = sc->max_mhz;
diff --git a/sys/sys/cpu.h b/sys/sys/cpu.h
index d282d300695f..c16091e1504e 100644
--- a/sys/sys/cpu.h
+++ b/sys/sys/cpu.h
@@ -36,6 +36,7 @@
  */
 
 #define CPU_IVAR_PCPU		1
+#define CPU_IVAR_NOMINAL_MHZ	2
 
 static __inline struct pcpu *cpu_get_pcpu(device_t dev)
 {
@@ -44,6 +45,15 @@ static __inline struct pcpu *cpu_get_pcpu(device_t dev)
 	return ((struct pcpu *)v);
 }
 
+static __inline int32_t cpu_get_nominal_mhz(device_t dev)
+{
+	uintptr_t v = 0;
+	if (BUS_READ_IVAR(device_get_parent(dev), dev,
+	    CPU_IVAR_NOMINAL_MHZ, &v) != 0)
+		return (-1);
+	return ((int32_t)v);
+}
+
 /*
  * CPU frequency control interface.
  */