diff --git a/physmap.c b/physmap.c
index 4ebfb06..3c3f27b 100644
--- a/physmap.c
+++ b/physmap.c
@@ -282,6 +282,8 @@
 			      PHYSMAP_RO);
 }
 
+/* MSR abstraction implementations for Linux, OpenBSD, FreeBSD/Dragonfly, OSX, libpayload
+ * and a non-working default implemenation on the bottom. See also hwaccess.h for some (re)declarations. */
 #if defined(__i386__) || defined(__x86_64__)
 
 #ifdef __linux__
@@ -381,8 +383,83 @@
 	/* Clear MSR file descriptor. */
 	fd_msr = -1;
 }
-#else
-#if defined(__FreeBSD__) || defined(__FreeBSD_kernel__) || defined(__DragonFly__)
+#elif defined(__OpenBSD__) /* This does only work for certain AMD Geode LX systems see amdmsr(4). */
+#include <sys/ioctl.h>
+#include <machine/amdmsr.h>
+
+static int fd_msr = -1;
+
+msr_t rdmsr(int addr)
+{
+	struct amdmsr_req args;
+
+	msr_t msr = { 0xffffffff, 0xffffffff };
+
+	args.addr = (uint32_t)addr;
+
+	if (ioctl(fd_msr, RDMSR, &args) < 0) {
+		msg_perr("Error while executing RDMSR ioctl: %s\n", strerror(errno));
+		close(fd_msr);
+		exit(1);
+	}
+
+	msr.lo = args.val & 0xffffffff;
+	msr.hi = args.val >> 32;
+
+	return msr;
+}
+
+int wrmsr(int addr, msr_t msr)
+{
+	struct amdmsr_req args;
+
+	args.addr = addr;
+	args.val = (((uint64_t)msr.hi) << 32) | msr.lo;
+
+	if (ioctl(fd_msr, WRMSR, &args) < 0) {
+		msg_perr("Error while executing WRMSR ioctl: %s\n", strerror(errno));
+		close(fd_msr);
+		exit(1);
+	}
+
+	return 0;
+}
+
+int setup_cpu_msr(int cpu)
+{
+	char msrfilename[64];
+	memset(msrfilename, 0, sizeof(msrfilename));
+	snprintf(msrfilename, sizeof(msrfilename), "/dev/amdmsr");
+
+	if (fd_msr != -1) {
+		msg_pinfo("MSR was already initialized\n");
+		return -1;
+	}
+
+	fd_msr = open(msrfilename, O_RDWR);
+
+	if (fd_msr < 0) {
+		msg_perr("Error while opening %s: %s\n", msrfilename, strerror(errno));
+		return -1;
+	}
+
+	return 0;
+}
+
+void cleanup_cpu_msr(void)
+{
+	if (fd_msr == -1) {
+		msg_pinfo("No MSR initialized.\n");
+		return;
+	}
+
+	close(fd_msr);
+
+	/* Clear MSR file descriptor. */
+	fd_msr = -1;
+}
+
+#elif defined(__FreeBSD__) || defined(__FreeBSD_kernel__) || defined(__DragonFly__)
 #include <sys/ioctl.h>
 
 typedef struct {
@@ -465,9 +542,8 @@
 	fd_msr = -1;
 }
 
-#else
-
-#if defined(__MACH__) && defined(__APPLE__)
+#elif defined(__MACH__) && defined(__APPLE__)
+/* rdmsr() and wrmsr() are provided by DirectHW which needs neither setup nor cleanup. */
 int setup_cpu_msr(int cpu)
 {
 	// Always succeed for now
@@ -494,6 +570,7 @@
 	return 0;
 }
 #else
+/* default MSR implementation */
 msr_t rdmsr(int addr)
 {
 	msr_t ret = { 0xffffffff, 0xffffffff };
@@ -516,9 +593,7 @@
 {
 	// Nothing, yet.
 }
-#endif
-#endif
-#endif
-#else
+#endif // OS switches for MSR code
+#else // x86
 /* Does MSR exist on non-x86 architectures? */
-#endif
+#endif // arch switches for MSR code