diff --git a/TODO b/TODO
index 352968a8e..43e309ac8 100644
--- a/TODO
+++ b/TODO
@@ -1,5 +1,4 @@
 TODO list:
-  - cache world calculation results
   - migrate server code to ServerInterface
   - Community repositories
   - find a way to better handle real smartapps deps (need split PDEPEND?)
diff --git a/libraries/databaseTools.py b/libraries/databaseTools.py
index 4feff7737..ecdcaa025 100644
--- a/libraries/databaseTools.py
+++ b/libraries/databaseTools.py
@@ -2313,9 +2313,6 @@ class etpDatabase(TextInterface):
 
     def retrieveNeeded(self, idpackage):
 
-	cache = self.fetchInfoCache(idpackage,'retrieveNeeded')
-	if cache != None: return cache
-
         try:
             self.cursor.execute('SELECT library FROM needed,neededreference WHERE needed.idpackage = (?) and needed.idneeded = neededreference.idneeded', (idpackage,))
         except:
@@ -2323,7 +2320,6 @@ class etpDatabase(TextInterface):
             self.cursor.execute('SELECT library FROM needed,neededreference WHERE needed.idpackage = (?) and needed.idneeded = neededreference.idneeded', (idpackage,))
         needed = self.fetchall2set(self.cursor.fetchall())
 
-	self.storeInfoCache(idpackage,'retrieveNeeded',needed)
 	return needed
 
     def retrieveConflicts(self, idpackage):
@@ -3202,6 +3198,17 @@ class etpDatabase(TextInterface):
         if rslt == None:
             raise exceptionTools.SystemDatabaseError("SystemDatabaseError: table extrainfo not found. Either does not exist or corrupted.")
 
+    def tablesChecksum(self):
+        import md5
+        self.cursor.execute('select * from baseinfo')
+        m = md5.new()
+        for row in self.cursor:
+            m.update(str(row))
+        self.cursor.execute('select * from dependenciesreference')
+        for row in self.cursor:
+            m.update(str(row))
+        return m.hexdigest()
+
 
 ########################################################
 ####
diff --git a/libraries/entropy.py b/libraries/entropy.py
index 69d383856..adb77eee2 100644
--- a/libraries/entropy.py
+++ b/libraries/entropy.py
@@ -268,6 +268,9 @@ class EquoInterface(TextInterface):
                                                 depend
                                         ), importance = 0, type = "info", back = True, count = (cnt, maxlen) )
             self.atomMatch(depend)
+
+        self.calculate_world_updates()
+
         self.updateProgress(darkred("Dependencies cache filled."), importance = 2, type = "warning")
         self.save_cache()
 
@@ -1199,13 +1202,28 @@ class EquoInterface(TextInterface):
         remove = set()
         fine = set()
 
+        if self.xcache:
+            db_digest = self.clientDbconn.tablesChecksum()
+            disk_cache = self.dumpTools.loadobj(etpCache['world_update'])
+            try:
+                if disk_cache != None:
+                    if disk_cache['db_digest'] == db_digest and \
+                        disk_cache['empty_deps'] == empty_deps and \
+                        disk_cache['branch'] == branch:
+                        return disk_cache['update'],disk_cache['remove'],disk_cache['fine']
+            except:
+                try:
+                    self.dumpTools.dumpobj(etpCache['world_update'], {})
+                except IOError:
+                    pass
+
         # get all the installed packages
         packages = self.clientDbconn.listAllPackages()
         maxlen = len(packages)
         count = 0
         for package in packages:
             count += 1
-            self.updateProgress("", importance = 0, type = "info", back = True, header = "::", count = (count,maxlen), percent = True, footer = "::")
+            self.updateProgress("Calculating world dependencies", importance = 0, type = "info", back = True, header = "::", count = (count,maxlen), percent = True, footer = "::")
             tainted = False
             atom = package[0]
             idpackage = package[1]
@@ -1258,6 +1276,22 @@ class EquoInterface(TextInterface):
                 fine.add(atom)
 
         del packages
+
+        if self.xcache:
+            try:
+                mycache = {}
+                mycache['db_digest'] = db_digest
+                mycache['update'] = update.copy()
+                mycache['remove'] = remove.copy()
+                mycache['fine'] = fine.copy()
+                mycache['empty_deps'] = empty_deps
+                mycache['branch'] = branch
+                # save cache
+                self.dumpTools.dumpobj(etpCache['world_update'], mycache)
+                mycache.clear()
+                del mycache
+            except:
+                self.dumpTools.dumpobj(etpCache['world_update'], {})
         return update, remove, fine
 
     # every tbz2 file that would be installed must pass from here
diff --git a/libraries/entropyConstants.py b/libraries/entropyConstants.py
index 3b3eaf956..5da4e1ba3 100644
--- a/libraries/entropyConstants.py
+++ b/libraries/entropyConstants.py
@@ -350,6 +350,7 @@ etpCache = {
     'install': 'resume_install', # resume cache (install)
     'remove': 'resume_remove', # resume cache (remove)
     'world': 'resume_world', # resume cache (world)
+    'world_update': 'world_cache'
 }
 
 # byte sizes of disk caches