diff --git a/devsupApp/src/Makefile b/devsupApp/src/Makefile
index 242646b..7e49fbe 100644
--- a/devsupApp/src/Makefile
+++ b/devsupApp/src/Makefile
@@ -74,6 +74,7 @@ softIocPy$(PY_VER)_LIBS += $(EPICS_BASE_IOC_LIBS)
 PY += devsup/__init__.py
 PY += devsup/_nullapi.py
 PY += devsup/db.py
+PY += devsup/dset.py
 PY += devsup/hooks.py
 PY += devsup/interfaces.py
 PY += devsup/util.py
diff --git a/devsupApp/src/devsup/dset.py b/devsupApp/src/devsup/dset.py
new file mode 100644
index 0000000..7680684
--- /dev/null
+++ b/devsupApp/src/devsup/dset.py
@@ -0,0 +1,117 @@
+# -*- coding: utf-8 -*-
+"""
+Some general purpose device supports
+"""
+
+import logging
+_log = logging.getLogger(__name__)
+
+import time
+from .hooks import initHook
+
+class AsyncOffload(object):
+    """A device support which off-loads processing to a worker thread.
+
+    >>> class ArrSum(AsyncOffload):
+        inputs = {'A':'one', 'B':'two'}
+        outputs= {'VALA':'result'}
+
+        def inThread(one=0, two=0):
+            return {'result':one+two}
+
+
+    The attribute "worker" may be set to an instance of Worker, either
+    statically, or in the derived class constructor (before calling the Base
+    class constructor).
+    If this attribute remains None, then a new Worker thread is created for
+    each record instance.
+
+    The attribute "scan" may similarly be set to an instance of IOScanListBlock.
+    
+    The "inputs" and "outputs" dictionary exist to map record Field names
+    to internal names.  This also serves to indicate which fields the inThread
+    methods may use.  This avoid processing of unnecesary (array) fields.
+    """
+
+    worker = None
+    scan = None
+
+    inputs = {}
+    outputs = {}
+    timefld = None
+
+    def __init__(self, rec, link):
+        self.rec, self.link = rec, link
+
+        if self.worker is None:
+            from devsup.util import Worker
+            self.worker = Worker(max=1)
+
+            @initHook('AtIocExit')
+            def _exit():
+                print 'stop worker for', rec.NAME
+                self.worker.join()
+    
+            self.worker.start()
+
+        assert self.worker is not None, "Offload requires a worker thread"
+
+        I = []
+        for fld,name in self.inputs.items():
+            F = rec.field(fld)
+            I.append((fld, name, F.fieldinfo()[2]!=1))
+
+        O = list(self.outputs.items())
+
+        self._inputs, self._outputs = I, O
+
+    def allowScan(self, rec):
+        if self.scan:
+            return self.scan.add(rec)
+
+    def detach(self, rec):
+        pass
+
+    def process(self, rec, reason=None):
+        if reason is None:
+            self._tstart = time.time()
+            
+            V = {}
+            for fld,name,arr in self._inputs:
+                val = getattr(rec, fld)
+                if arr:
+                    val = val.copy()
+                V[name] = val
+
+            self.worker.add(self._wrap, args=(rec,), kws=V)
+
+            rec.asyncStart()
+
+        else:
+            result = reason
+            if result['ok']:
+                for fld,name in self._outputs:
+                    setattr(rec, fld, result.get(name, 0))
+
+                sevr = result.get('severity', 0)
+                if sevr:
+                    rec.setSevr(sevr)
+
+            else:
+                rec.setSevr()
+
+            self._tend = time.time()
+            if self.timefld:
+                setattr(rec, self.timefld, self._tend-self._tstart)
+
+    def _wrap(self, rec, **kws):
+        try:
+            result = self.inThread(**kws)
+            result.setdefault('ok', True)
+            rec.asyncFinish(reason=result)
+        except:
+            _log.exception('Error while processing %s', rec.NAME)
+            rec.asyncFinish(reason={'ok':False})
+
+    def inThread(self, **kws):
+        return {'ok':False}