diff --git a/includes/backend.inc b/includes/backend.inc
index bd1eb12..7c5c3d4 100644
--- a/includes/backend.inc
+++ b/includes/backend.inc
@@ -334,8 +334,10 @@ function _drush_backend_proc_open($cmds, $process_limit, $context = NULL) {
   $open_processes = array();
   $bucket = array();
   $process_limit = max($process_limit, 1);
-  // Loop through processes until they all close.
+  // Loop through processes until they all close, having a nap as needed.
+  $nap_time = 0;
   while (sizeof($open_processes) || sizeof($cmds)) {
+    $nap_time++;
     if (sizeof($cmds) && (sizeof($open_processes) < $process_limit)) {
       // Pop the site and command (key / value) from the cmds array
       end($cmds);
@@ -376,6 +378,9 @@ function _drush_backend_proc_open($cmds, $process_limit, $context = NULL) {
         $bucket[$site]['outputted'] = FALSE;
         $open_processes[$site] = $process;
       }
+      // Reset the $nap_time variable as there might be output to process next
+      // time around:
+      $nap_time = 0;
     }
     foreach ($open_processes as $site => &$current_process) {
       if (isset($current_process['pipes'][1])) {
@@ -407,19 +412,39 @@ function _drush_backend_proc_open($cmds, $process_limit, $context = NULL) {
           $bucket[$site]['output'] .= $string;
           $info = stream_get_meta_data($current_process['pipes'][1]);
           flush();
+
+          // Reset the $nap_time variable as there might be output to process
+          // next time around:
+          if (!empty($string)) {
+            $nap_time = 0;
+          }
         }
         else {
           fclose($current_process['pipes'][1]);
           unset($current_process['pipes'][1]);
           // close the pipe , set a marker
+
+          // Reset the $nap_time variable as there might be output to process
+          // next time around:
+          $nap_time = 0;
         }
       }
       else {
         // if both pipes are closed for the process, remove it from active loop and add a new process to open.
         $bucket[$site]['code'] = proc_close($current_process['process']);
         unset($open_processes[$site]);
+
+        // Reset the $nap_time variable as there might be output to process next
+        // time around:
+        $nap_time = 0;
       }
     }
+
+    // We should sleep for a bit if we need to, up to a maximum of 1/10 of a
+    // second.
+    if ($nap_time > 0) {
+      usleep(max($nap_time * 500, 100000));
+    }
   }
   return $bucket;
   // TODO: Handle bad proc handles