diff -ur jack-audio-connection-kit-0.100.7/config/os/generic/time.h jack/config/os/generic/time.h
--- jack-audio-connection-kit-0.100.7/config/os/generic/time.h	2004-04-07 07:52:58.000000000 +0300
+++ jack/config/os/generic/time.h	2005-12-06 12:24:03.000000000 +0200
@@ -1,5 +1,6 @@
 /*
     Copyright (C) 2001-2004 Paul Davis, Tilman Linneweh
+    Copyright (C) 2005 Jussi Laako
 
     Generic version, overridden by OS-specific definition when needed.
     
@@ -23,48 +24,24 @@
 #define __jack_time_h__
 
 #include <stdio.h>
+#include <sys/time.h>
 #include <jack/internal.h>
-#include <sysdeps/cycles.h>
-
-/* This is a kludge.  We need one global instantiation of this
- * variable in each address space.  So, libjack/client.c declares the
- * actual storage.  Other source files will see it as an extern. */
-#define JACK_TIME_GLOBAL_DECL jack_time_t __jack_cpu_mhz
-extern JACK_TIME_GLOBAL_DECL;
 
 static inline jack_time_t 
 jack_get_microseconds (void) {
-	return get_cycles() / __jack_cpu_mhz;
-}
+	jack_time_t jackTime;
+	struct timeval time;
 
-/* This function is inspired by similar code in MPLayer.
- * It should be quite portable
- */
-static inline jack_time_t
-jack_get_mhz (void)
-{
-       jack_time_t tsc_start, tsc_end;
-       struct timeval tv_start, tv_end;
-       long usec_delay;
-       jack_time_t mhz;
-                     
-       tsc_start = get_cycles();   
-       gettimeofday(&tv_start, NULL);
-       usleep(100000);
-       tsc_end = get_cycles();
-       gettimeofday(&tv_end, NULL);
-                
-       usec_delay = 1000000 * (tv_end.tv_sec - tv_start.tv_sec)
-           + (tv_end.tv_usec - tv_start.tv_usec);
-       mhz = (tsc_end - tsc_start) / usec_delay;
-       return mhz;
+	gettimeofday(&time, NULL);
+	jackTime = (jack_time_t) time.tv_sec * 1e6 +
+		(jack_time_t) time.tv_usec;
+	return jackTime;
 }
 
 /* This should only be called ONCE per process. */
 static inline void 
 jack_init_time ()
 {
-	__jack_cpu_mhz = jack_get_mhz ();
 }
 
 #endif /* __jack_time_h__ */
diff -ur jack-audio-connection-kit-0.100.7/config/os/gnu-linux/time.h jack/config/os/gnu-linux/time.h
--- jack-audio-connection-kit-0.100.7/config/os/gnu-linux/time.h	2004-03-25 21:31:44.000000000 +0200
+++ jack/config/os/gnu-linux/time.h	2005-12-06 16:30:20.000000000 +0200
@@ -1,5 +1,6 @@
 /*
     Copyright (C) 2001-2003 Paul Davis
+    Copyright (C) 2005 Jussi Laako
 
     This is the GNU/Linux version.
     
@@ -23,18 +24,35 @@
 #define __jack_time_h__
 
 #include <stdio.h>
+#include <time.h>
+#include <sys/time.h>
 #include <jack/internal.h>
 #include <sysdeps/cycles.h>
 
-/* This is a kludge.  We need one global instantiation of this
- * variable in each address space.  So, libjack/client.c declares the
- * actual storage.  Other source files will see it as an extern. */
+/* This is a kludge.  We need one global instantiation of these
+ * variables in each address space.  So, libjack/client.c declares the
+ * actual storage.  Other source files will see those as an externs. */
 #define JACK_TIME_GLOBAL_DECL jack_time_t __jack_cpu_mhz
+#define JACK_TIME_SOURCE_DECL int __jack_clock_source
+#define JACK_TIME_FUNC_DECL jack_time_t (*jack_get_microseconds) (void)
 extern JACK_TIME_GLOBAL_DECL;
+extern JACK_TIME_SOURCE_DECL;
+extern JACK_TIME_FUNC_DECL;
 
-static inline jack_time_t 
-jack_get_microseconds (void) {
-	return get_cycles() / __jack_cpu_mhz;
+static jack_time_t 
+jack_get_microseconds0 (void) {
+	jack_time_t jackTime;
+	struct timespec time;
+
+	clock_gettime(CLOCK_MONOTONIC, &time);
+	jackTime = (jack_time_t) time.tv_sec * 1e6 +
+		(jack_time_t) time.tv_nsec / 1e3;
+	return jackTime;
+}
+
+static jack_time_t 
+jack_get_microseconds1 (void) {
+		return get_cycles() / __jack_cpu_mhz;
 }
 
 /*
@@ -94,4 +112,21 @@
 	__jack_cpu_mhz = jack_get_mhz ();
 }
 
+/* Set time function. */
+static inline void
+jack_set_clock_source (int clocksrc)
+{
+	__jack_clock_source = clocksrc;
+	switch (__jack_clock_source)
+	{
+		case 1:
+			jack_get_microseconds = jack_get_microseconds1;
+			break;
+		case 0:
+		default:
+			jack_get_microseconds = jack_get_microseconds0;
+			break;
+	}
+}
+
 #endif /* __jack_time_h__ */
diff -ur jack-audio-connection-kit-0.100.7/configure.ac jack/configure.ac
--- jack-audio-connection-kit-0.100.7/configure.ac	2005-10-30 13:01:31.000000000 +0200
+++ jack/configure.ac	2005-12-06 14:13:09.000000000 +0200
@@ -126,6 +126,7 @@
 AC_CHECK_FUNCS(on_exit atexit)
 AC_CHECK_FUNCS(posix_memalign)
 AC_CHECK_LIB(m, sin)
+AC_CHECK_FUNC(clock_gettime, [], AC_CHECK_LIB(rt, clock_gettime))
 
 # should we use mlockall() on this platform?
 if test "x$JACK_DO_NOT_MLOCK" = "x"; then
diff -ur jack-audio-connection-kit-0.100.7/jack/engine.h jack/jack/engine.h
--- jack-audio-connection-kit-0.100.7/jack/engine.h	2004-12-19 20:41:28.000000000 +0200
+++ jack/jack/engine.h	2005-12-06 13:47:39.000000000 +0200
@@ -169,6 +169,8 @@
 int		jack_get_fifo_fd (jack_engine_t *engine,
 				  unsigned int which_fifo);
 
+extern int clock_source;
+
 extern jack_client_internal_t *
 jack_client_internal_by_id (jack_engine_t *engine, jack_client_id_t id);
 
diff -ur jack-audio-connection-kit-0.100.7/jack/internal.h jack/jack/internal.h
--- jack-audio-connection-kit-0.100.7/jack/internal.h	2005-08-22 23:48:24.000000000 +0300
+++ jack/jack/internal.h	2005-12-06 13:50:48.000000000 +0200
@@ -130,6 +130,7 @@
     jack_time_t           sync_time_left;
     jack_frame_timer_t    frame_timer;
     int32_t		  internal;
+    int                   clock_source;
     pid_t                 engine_pid;
     jack_nframes_t	  buffer_size;
     int8_t		  real_time;
diff -ur jack-audio-connection-kit-0.100.7/jackd/engine.c jack/jackd/engine.c
--- jack-audio-connection-kit-0.100.7/jackd/engine.c	2005-06-15 12:18:40.000000000 +0300
+++ jack/jackd/engine.c	2005-12-06 16:21:50.000000000 +0200
@@ -78,6 +78,8 @@
     dlhandle       handle;
 } jack_driver_info_t;
 
+int clock_source = 0;
+
 static int                    jack_port_assign_buffer (jack_engine_t *,
 						       jack_port_internal_t *);
 static jack_port_internal_t *jack_get_port_by_name (jack_engine_t *,
@@ -1679,6 +1681,13 @@
 	engine->control->xrun_delayed_usecs = 0;
 	engine->control->max_delayed_usecs = 0;
 
+#ifdef JACK_TIME_FUNC_DECL
+	jack_set_clock_source(clock_source);
+#else
+	__jack_clock_source = clock_source;
+#endif
+	engine->control->clock_source = clock_source;
+
 	engine->control->frame_timer.frames = 0;
 	engine->control->frame_timer.reset_pending = 0;
 	engine->control->frame_timer.current_wakeup = 0;
diff -ur jack-audio-connection-kit-0.100.7/jackd/jackd.c jack/jackd/jackd.c
--- jack-audio-connection-kit-0.100.7/jackd/jackd.c	2005-06-15 12:18:40.000000000 +0300
+++ jack/jackd/jackd.c	2005-12-06 13:52:15.000000000 +0200
@@ -368,6 +368,7 @@
 "             [ --verbose OR -v ]\n"
 "             [ --silent OR -s ]\n"
 "             [ --version OR -V ]\n"
+"             [ --clock-source OR -c ]\n"
 "         -d driver [ ... driver args ... ]\n"
 "             where driver can be `alsa', `coreaudio', `dummy',\n"
 "                                 `oss' or `portaudio'\n\n"
@@ -463,7 +464,7 @@
 
 {
 	jack_driver_desc_t * desc;
-	const char *options = "-ad:P:uvshVRTFl:t:mn:p:";
+	const char *options = "-ad:P:uvshVRTFl:t:mn:p:c:";
 	struct option long_options[] = 
 	{ 
 		{ "driver", 1, 0, 'd' },
@@ -479,6 +480,7 @@
 		{ "temporary", 0, 0, 'T' },
 		{ "version", 0, 0, 'V' },
 		{ "silent", 0, 0, 's' },
+		{ "clock-source", 1, 0, 'c' },
 		{ 0, 0, 0, 0 }
 	};
 	int opt = 0;
@@ -586,6 +588,10 @@
 			show_version = 1;
 			break;
 
+		case 'c':
+			clock_source = atoi (optarg);
+			break;
+
 		default:
 			fprintf (stderr, "unknown option character %c\n",
 				 optopt);
diff -ur jack-audio-connection-kit-0.100.7/libjack/client.c jack/libjack/client.c
--- jack-audio-connection-kit-0.100.7/libjack/client.c	2005-09-11 02:58:43.000000000 +0300
+++ jack/libjack/client.c	2005-12-06 16:21:12.000000000 +0200
@@ -51,6 +51,10 @@
 
 #include <sysdeps/time.h>
 JACK_TIME_GLOBAL_DECL;			/* One instance per process. */
+JACK_TIME_SOURCE_DECL;			/* One instance per process. */
+#ifdef JACK_TIME_FUNC_DECL
+JACK_TIME_FUNC_DECL;
+#endif
 
 #include "local.h"
 
@@ -959,6 +963,13 @@
 	
 	client->engine = (jack_control_t *) jack_shm_addr (&client->engine_shm);
 
+	/* initialize clock source as early as possible */
+#ifdef JACK_TIME_FUNC_DECL
+	jack_set_clock_source(client->engine->clock_source);
+#else
+	__jack_clock_source = client->engine->clock_source;
+#endif
+
 	/* now attach the client control block */
 	client->control_shm = res.client_shm;
 	if (jack_attach_shm (&client->control_shm)) {
