diff --git a/sys/amd64/amd64/amd64_mem.c b/sys/amd64/amd64/amd64_mem.c
index fcff3cee6bd..589fc64721c 100644
--- a/sys/amd64/amd64/amd64_mem.c
+++ b/sys/amd64/amd64/amd64_mem.c
@@ -32,6 +32,7 @@
 #include <sys/malloc.h>
 #include <sys/memrange.h>
 #include <sys/smp.h>
+#include <sys/sysctl.h>
 
 #include <machine/md_var.h>
 #include <machine/specialreg.h>
@@ -60,6 +61,11 @@ static char *mem_owner_bios = "BIOS";
 
 #define mrcopyflags(curr, new) (((curr) & ~MDF_ATTRMASK) | ((new) & MDF_ATTRMASK))
 
+static int			mtrrs_disabled;
+TUNABLE_INT("machdep.disable_mtrrs", &mtrrs_disabled);
+SYSCTL_INT(_machdep, OID_AUTO, disable_mtrrs, CTLFLAG_RD,
+	&mtrrs_disabled, 0, "Disable i686 MTRRs.");
+
 static void			i686_mrinit(struct mem_range_softc *sc);
 static int			i686_mrset(struct mem_range_softc *sc,
 					   struct mem_range_desc *mrd,
@@ -601,7 +607,7 @@ static void
 i686_mem_drvinit(void *unused)
 {
     /* Try for i686 MTRRs */
-    if ((cpu_feature & CPUID_MTRR) &&
+    if (!mtrrs_disabled && (cpu_feature & CPUID_MTRR) &&
 	((cpu_id & 0xf00) == 0x600 || (cpu_id & 0xf00) == 0xf00) &&
 	((strcmp(cpu_vendor, "GenuineIntel") == 0) ||
 	(strcmp(cpu_vendor, "AuthenticAMD") == 0))) {
diff --git a/sys/boot/common/help.common b/sys/boot/common/help.common
index c97ba414e79..ad30a33cde8 100644
--- a/sys/boot/common/help.common
+++ b/sys/boot/common/help.common
@@ -256,6 +256,10 @@
 
 		Disable the use of the PCI BIOS (i386 only)
 
+	set machdep.disable_mtrrs=1
+
+		Disable the use of i686 MTRRs (i386 only)
+
 	set net.inet.tcp.tcbhashsize=<value>	TCBHASHSIZE
 
 		Overrides the compile-time set value of TCBHASHSIZE or
diff --git a/sys/boot/common/loader.8 b/sys/boot/common/loader.8
index a76e691031d..a32be170bf4 100644
--- a/sys/boot/common/loader.8
+++ b/sys/boot/common/loader.8
@@ -476,6 +476,8 @@ Note that
 the NBUF parameter will override this limit.
 Modifies
 .Va VM_BCACHE_SIZE_MAX .
+.It Va machdep.disable_mtrrs
+Disable the use of i686 MTRRs (x86 only).
 .It Va machdep.pccard.pcic_irq
 Overrides the IRQ normally assigned to a PCCARD controller.
 Typically the first available interrupt will be allocated,
diff --git a/sys/i386/i386/i686_mem.c b/sys/i386/i386/i686_mem.c
index fcff3cee6bd..589fc64721c 100644
--- a/sys/i386/i386/i686_mem.c
+++ b/sys/i386/i386/i686_mem.c
@@ -32,6 +32,7 @@
 #include <sys/malloc.h>
 #include <sys/memrange.h>
 #include <sys/smp.h>
+#include <sys/sysctl.h>
 
 #include <machine/md_var.h>
 #include <machine/specialreg.h>
@@ -60,6 +61,11 @@ static char *mem_owner_bios = "BIOS";
 
 #define mrcopyflags(curr, new) (((curr) & ~MDF_ATTRMASK) | ((new) & MDF_ATTRMASK))
 
+static int			mtrrs_disabled;
+TUNABLE_INT("machdep.disable_mtrrs", &mtrrs_disabled);
+SYSCTL_INT(_machdep, OID_AUTO, disable_mtrrs, CTLFLAG_RD,
+	&mtrrs_disabled, 0, "Disable i686 MTRRs.");
+
 static void			i686_mrinit(struct mem_range_softc *sc);
 static int			i686_mrset(struct mem_range_softc *sc,
 					   struct mem_range_desc *mrd,
@@ -601,7 +607,7 @@ static void
 i686_mem_drvinit(void *unused)
 {
     /* Try for i686 MTRRs */
-    if ((cpu_feature & CPUID_MTRR) &&
+    if (!mtrrs_disabled && (cpu_feature & CPUID_MTRR) &&
 	((cpu_id & 0xf00) == 0x600 || (cpu_id & 0xf00) == 0xf00) &&
 	((strcmp(cpu_vendor, "GenuineIntel") == 0) ||
 	(strcmp(cpu_vendor, "AuthenticAMD") == 0))) {