diff --git a/Makefile.target b/Makefile.target
index 8c7a072..b7f6c4c 100644
--- a/Makefile.target
+++ b/Makefile.target
@@ -103,6 +103,9 @@ obj-$(CONFIG_LIBDECNUMBER) += libdecnumber/dpd/decimal32.o
 obj-$(CONFIG_LIBDECNUMBER) += libdecnumber/dpd/decimal64.o
 obj-$(CONFIG_LIBDECNUMBER) += libdecnumber/dpd/decimal128.o
 
+# qqq
+obj-y += qqq.o
+
 #########################################################
 # Linux user emulator target
 
diff --git a/docs/simulation-sync.txt b/docs/simulation-sync.txt
new file mode 100644
index 0000000..2133093
--- /dev/null
+++ b/docs/simulation-sync.txt
@@ -0,0 +1,60 @@
+= Synchronizing the virtual clock with an external source =
+
+QEMU has a protocol for synchronizing its virtual clock
+with the clock of a simulator in which QEMU is embedded
+as a component. This options is enabled with the -qqq
+argument, and it should generally be accompanied by the
+following additional command line arguments:
+
+-icount 1,sleep=off -rtc clock=vm
+
+The -qqq argument is used to supply file descriptors
+for two Unix pipes. The read pipe is used by QEMU to
+receive synchronization data from the external simulator.
+The write pipe is used by QEMU to supply synchronization
+data to the external emulator. The typical procedure for
+launching QEMU in is synchronization mode has three steps:
+
+(1) Create two pairs of pipes with the Linux pipe function.
+    The code segment that does this might look like
+
+       int pipefd1[2];
+       int pipefd2[2];
+       pipe(pipefd1);
+       pipe(pipefd2);
+
+(2) Fork QEMU with the appropriate command line arguments.
+    The -qqq part of the argument will look something like
+
+       -qqq write=pipefd1[1],read=pipefd2[0]
+
+(3) After forking QEMU, close pipefd1[1] and pipefd2[0].
+    Retain the other pair of pipes for communicating with QEMU.
+
+The synchronization protocol is very simple. To start, the
+external simulator writes an integer to its write pipe with
+the amount of time in microseconds that QEMU is allowed to
+advance. The code segment that does this might look like:
+
+    int ta = 1000; // Advance by 1 millisecond
+    write(pipefd2[1],&ta,sizeof(int));
+
+The external simulator can then advance its clock by this
+same amount. During this time, QEMU and the external simulator
+will be executing in parallel. When the external simulator
+completes its time advance, it waits for QEMU by reading from
+its read pipe. The value read will be the actual number of
+virtual microseconds by which QEMU has advanced its virtual clock.
+This will be greater than or equal to the requested advance.
+The code that does this might look like:
+
+   read(pipefd1[0],&ta,sizeof(int));
+
+These steps are repeated until either (1) the external simulator
+closes its pipes thereby causing QEMU to terminate or (2) QEMU
+stops executing (e.g., if the emulated computer is shutdown) and
+causes SIGPIPE to be generated by the closing of its pipes.
+
+You can find an example of a simulator using this protocol in
+the adevs simulation package at http://sourceforge.net/projects/adevs/
+
diff --git a/qemu-options.hx b/qemu-options.hx
index a71aaf8..d52cc9c 100644
--- a/qemu-options.hx
+++ b/qemu-options.hx
@@ -3359,6 +3359,22 @@ many timer interrupts were not processed by the Windows guest and will
 re-inject them.
 ETEXI
 
+DEF("qqq", HAS_ARG, QEMU_OPTION_qqq, \
+    "-qqq read=fd,write=fd\n" \
+    "                enable synchronization of the virtual clock \n" \
+    "                with an external simulation clock\n", QEMU_ARCH_ALL)
+STEXI
+@item -qqq read=@var{fd0},write=@var{fd1}
+@findex -qqq
+Qemu will use the supplied pipes to synchronize its virtual clock with
+an external simulation clock. Qemu will wait until a time slice size in
+microseconds is supplied on the read pipe. Then it will execute for at
+least that number of virtual microseconds before writing the actual
+virtual time that has elapsed in microseconds to the write pipe. This
+cycle will repeat until a zero is elaspsed time is requested, which
+will cause qemu to exit.
+ETEXI
+
 DEF("icount", HAS_ARG, QEMU_OPTION_icount, \
     "-icount [shift=N|auto][,align=on|off][,sleep=on|off,rr=record|replay,rrfile=<filename>]\n" \
     "                enable virtual instruction counter with 2^N clock ticks per\n" \
diff --git a/qqq.c b/qqq.c
new file mode 100644
index 0000000..bddfc71
--- /dev/null
+++ b/qqq.c
@@ -0,0 +1,109 @@
+
+#include "qemu/osdep.h"
+#include "qemu/timer.h"
+#include "qemu/main-loop.h"
+#include "sysemu/cpus.h"
+#include "qqq.h"
+#include <time.h>
+
+/* This is a Linux only feature */
+
+#ifndef _WIN32
+
+#include <unistd.h>
+#include <assert.h>
+
+static int elapsed = 0;
+static int time_advance = -1;
+static int read_fd = -1, write_fd = -1;
+static int64_t t;
+static QEMUTimer *sync_timer;
+
+static void cleanup_and_exit(void)
+{
+    close(read_fd);
+    close(write_fd);
+    exit(0);
+}
+
+static void write_mem_value(int val)
+{
+    if (write(write_fd, &val, sizeof(int)) != sizeof(int)) {
+        /* If the pipe is no good, then assume this is an
+         * indication that we should exit.
+         */
+        cleanup_and_exit();
+    }
+}
+
+static int read_mem_value(void)
+{
+    int tmp;
+    if (read(read_fd, &tmp, sizeof(int)) != sizeof(int)) {
+        /* If the pipe is no good, then assume this is an
+         * indication that we should exit.
+         */
+        cleanup_and_exit();
+    }
+    return tmp;
+}
+
+static void schedule_next_event(void)
+{
+    /* If we got the time advance in fd_read, then don't do it
+     * again here. */
+    if (time_advance < 0) {
+        /* Otherwise read the value from the pipe */
+        time_advance = read_mem_value();
+    }
+    /* Schedule the next synchronization point */
+    timer_mod(sync_timer, t + time_advance);
+    /* Note that we need to read the time advance again on the next pass */
+    time_advance = -1;
+}
+
+static void sync_func(void *data)
+{
+    /* Report the actual elapsed time. */
+    int64_t tnow = qemu_clock_get_us(QEMU_CLOCK_VIRTUAL);
+    elapsed = tnow - t;
+    write_mem_value(elapsed);
+    /* Update our time of last event */
+    t = tnow;
+    /* Schedule the next event */
+    schedule_next_event();
+}
+
+static void fd_read(void* opaque)
+{
+    /* Read the time advance if its becomes available
+     * before our timer expires */
+    time_advance = read_mem_value();
+} 
+
+void setup_qqq(QemuOpts *opts)
+{
+    /* Initialize the simulation clock */
+    t = 0;
+    /* Get the communication pipes */
+    read_fd = qemu_opt_get_number(opts, "read", 0);
+    write_fd = qemu_opt_get_number(opts, "write", 0);
+    /* Start the timer to ensure time warps advance the clock */
+    sync_timer = timer_new_us(QEMU_CLOCK_VIRTUAL, sync_func, NULL);
+    /* Get the time advance that is requested by the simulation */
+    schedule_next_event();
+    /* Register the file descriptor with qemu. This should ensure
+     * the emulator doesn't pause for lack of I/O and thereby
+     * cause the attached simulator to pause with it. */
+    qemu_set_fd_handler(read_fd,fd_read,NULL,NULL);
+}
+
+#else
+
+void setup_qqq(QemuOpts *opts)
+{
+    fprintf(stderr, "-qqq is not supported on Windows, exiting\n");
+    exit(0);
+}
+
+#endif
diff --git a/qqq.h b/qqq.h
new file mode 100644
index 0000000..40a24e3
--- /dev/null
+++ b/qqq.h
@@ -0,0 +1,35 @@
+/*
+ * This work is licensed under the terms of the GNU GPL
+ * version 2. Seethe COPYING file in the top-level directory.
+ *
+ * A module for pacing the rate of advance of the computer
+ * clock in reference to an external simulation clock. The
+ * basic approach used here is adapted from QBox from Green
+ * Socs. The mode of operation is as follows:
+ *
+ * The simulator uses pipes to exchange time advance data.
+ * The external simulator starts the exchange by forking a
+ * QEMU process and passing is descriptors for a read and
+ * write pipe. Then the external simulator writes an integer
+ * (native endian) to the pipe to indicate the number of
+ * microseconds that QEMU should advance. QEMU advances its
+ * virtual clock by this amount and writes to its write pipe
+ * the actual number of microseconds that have advanced.
+ * This process continues until a pipe on either side is
+ * closed, which will either cause QEMU to exit (if the
+ * external simulator closes a pipe) or raise SIGPIPE in the
+ * external simulator (if QEMU closes a pipe).
+ *
+ * Authors:
+ *   James Nutaro <nutaro@gmail.com>
+ *
+ */
+#ifndef QQQ_H
+#define QQQ_H
+
+#include "qemu/osdep.h"
+#include "qemu-options.h"
+
+void setup_qqq(QemuOpts *opts);
+
+#endif
diff --git a/vl.c b/vl.c
index ee557a1..3f2f9a3 100644
--- a/vl.c
+++ b/vl.c
@@ -122,6 +122,8 @@ int main(int argc, char **argv)
 #include "sysemu/replay.h"
 #include "qapi/qmp/qerror.h"
 
+#include "qqq.h"
+
 #define MAX_VIRTIO_CONSOLES 1
 #define MAX_SCLP_CONSOLES 1
 
@@ -231,6 +233,23 @@ static struct {
     { .driver = "virtio-vga",           .flag = &default_vga       },
 };
 
+static QemuOptsList qemu_qqq_opts = {
+    .name = "qqq",
+    .implied_opt_name = "",
+    .merge_lists = true,
+    .head = QTAILQ_HEAD_INITIALIZER(qemu_qqq_opts.head),
+    .desc = {
+        {
+            .name = "read",
+            .type = QEMU_OPT_NUMBER,
+        }, {
+            .name = "write",
+            .type = QEMU_OPT_NUMBER,
+        },
+        { /* end of list */ }
+    },
+};
+
 static QemuOptsList qemu_rtc_opts = {
     .name = "rtc",
     .head = QTAILQ_HEAD_INITIALIZER(qemu_rtc_opts.head),
@@ -2951,7 +2970,7 @@ int main(int argc, char **argv, char **envp)
     const char *boot_once = NULL;
     DisplayState *ds;
     int cyls, heads, secs, translation;
-    QemuOpts *hda_opts = NULL, *opts, *machine_opts, *icount_opts = NULL;
+    QemuOpts *hda_opts = NULL, *opts, *machine_opts, *icount_opts = NULL, *qqq_opts = NULL;
     QemuOptsList *olist;
     int optind;
     const char *optarg;
@@ -2987,6 +3006,7 @@ int main(int argc, char **argv, char **envp)
 
     module_call_init(MODULE_INIT_QOM);
 
+    qemu_add_opts(&qemu_qqq_opts);
     qemu_add_opts(&qemu_drive_opts);
     qemu_add_drive_opts(&qemu_legacy_drive_opts);
     qemu_add_drive_opts(&qemu_common_drive_opts);
@@ -3847,6 +3867,13 @@ int main(int argc, char **argv, char **envp)
                     exit(1);
                 }
                 break;
+            case QEMU_OPTION_qqq:
+                qqq_opts = qemu_opts_parse_noisily(qemu_find_opts("qqq"),
+                                                      optarg, true);
+                if (!qqq_opts) {
+                    exit(1);
+                }
+                break;
             case QEMU_OPTION_incoming:
                 if (!incoming) {
                     runstate_set(RUN_STATE_INMIGRATE);
@@ -4350,6 +4377,10 @@ int main(int argc, char **argv, char **envp)
     /* spice needs the timers to be initialized by this point */
     qemu_spice_init();
 
+    if (qqq_opts) {
+        setup_qqq(qqq_opts);
+    }
+
     cpu_ticks_init();
     if (icount_opts) {
         if (kvm_enabled() || xen_enabled()) {
