diff --git a/src/devedeng/configuration_data.py b/src/devedeng/configuration_data.py
index 4b6fa50..4ee9047 100644
--- a/src/devedeng/configuration_data.py
+++ b/src/devedeng/configuration_data.py
@@ -102,7 +102,9 @@ class configuration(GObject.GObject):
 
         self.PAL = True
         self.tmp_folder = "/var/tmp"
-        self.multicore = self.cores
+        # default to all-but-one core so a big parallel batch leaves the
+        # desktop responsive; the user can raise this in Preferences
+        self.multicore = max(1, self.cores - 1)
         self.final_folder = os.environ.get("HOME")
         self.sub_language = None
         self.sub_codepage = None