diff --git a/2.10/Source/FormRender.dfm b/2.10/Source/FormRender.dfm
index 4e56252..641f7dd 100644
--- a/2.10/Source/FormRender.dfm
+++ b/2.10/Source/FormRender.dfm
@@ -562,6 +562,15 @@ object RenderForm: TRenderForm
       end
     end
   end
+  object chkThreadPriority: TCheckBox
+    Left = 176
+    Top = 358
+    Width = 73
+    Height = 17
+    Caption = 'Low priority'
+    TabOrder = 10
+    OnClick = chkThreadPriorityClick
+  end
   object SaveDialog: TSaveDialog
     Left = 136
     Top = 360
diff --git a/2.10/Source/FormRender.pas b/2.10/Source/FormRender.pas
index 8a3baff..d048e2c 100644
--- a/2.10/Source/FormRender.pas
+++ b/2.10/Source/FormRender.pas
@@ -74,6 +74,7 @@ type
     chkLimitMem: TCheckBox;
     cbBitsPerSample: TComboBox;
     Output: TMemo;
+    chkThreadPriority: TCheckBox;
     procedure FormCreate(Sender: TObject);
     procedure FormDestroy(Sender: TObject);
     procedure btnRenderClick(Sender: TObject);
@@ -96,6 +97,7 @@ type
     procedure chkMaintainClick(Sender: TObject);
     procedure chkSaveIncompleteRendersClick(Sender: TObject);
     procedure cbBitsPerSampleSelect(Sender: TObject);
+    procedure chkThreadPriorityClick(Sender: TObject);
   private
     StartTime, EndTime, oldElapsed, edt: TDateTime;
     oldProg: double;
@@ -510,6 +512,11 @@ begin
         Renderer := TRenderThread.Create;
         assert(Renderer <> nil);
 
+        if chkThreadPriority.Checked then
+          Renderer.SetPriority(tpLower)
+        else
+          Renderer.SetPriority(tpNormal);
+
         Renderer.BitsPerSample := BitsPerSample;
         if chkLimitMem.checked then
           Renderer.MaxMem := MaxMemory;//StrToInt(cbMaxMemory.text);
@@ -577,6 +584,12 @@ begin
 
       Renderer := TRenderThread.Create;
       assert(Renderer <> nil);
+
+      if chkThreadPriority.Checked then
+        Renderer.SetPriority(tpLower)
+      else
+        Renderer.SetPriority(tpNormal);
+
       Renderer.BitsPerSample := BitsPerSample;
       if chkLimitMem.checked then
         Renderer.MaxMem := MaxMemory;//StrToInt(cbMaxMemory.text);
@@ -640,6 +653,7 @@ begin
   ShowMemoryStatus;
   Ratio := ImageWidth / ImageHeight;
   chkSaveIncompleteRenders.Checked := SaveIncompleteRenders;
+  chkThreadPriority.Checked := LowerRenderPriority;
 end;
 
 procedure TRenderForm.txtWidthChange(Sender: TObject);
@@ -1038,5 +1052,17 @@ begin
   ShowMemoryStatus;
 end;
 
+procedure TRenderForm.chkThreadPriorityClick(Sender: TObject);
+begin
+  LowerRenderPriority := chkThreadPriority.Checked;
+
+  if Assigned(Renderer) then begin
+    if LowerRenderPriority then
+      Renderer.SetPriority(tpLower)
+    else
+      Renderer.SetPriority(tpNormal);
+  end;
+end;
+
 end.
 
diff --git a/2.10/Source/Global.pas b/2.10/Source/Global.pas
index 0a2b8a6..57518d2 100644
--- a/2.10/Source/Global.pas
+++ b/2.10/Source/Global.pas
@@ -151,6 +151,7 @@ var
 
   SaveIncompleteRenders: boolean;
   ShowRenderStats: boolean;
+  LowerRenderPriority: boolean;
 
   SymmetryType: integer;
   SymmetryOrder: integer;
diff --git a/2.10/Source/Regstry.pas b/2.10/Source/Regstry.pas
index 3f5f702..63f8067 100644
--- a/2.10/Source/Regstry.pas
+++ b/2.10/Source/Regstry.pas
@@ -556,6 +556,7 @@ begin
         ShowProgress := true;
       end;
 
+      { FormRender }
       if Registry.ValueExists('SaveIncompleteRenders') then begin
         SaveIncompleteRenders := Registry.ReadBool('SaveIncompleteRenders');
       end else begin
@@ -566,6 +567,11 @@ begin
       end else begin
         ShowRenderStats := false;
       end;
+      if Registry.ValueExists('LowerRenderPriority') then begin
+        LowerRenderPriority := Registry.ReadBool('LowerRenderPriority');
+      end else begin
+        LowerRenderPriority := false;
+      end;
 
       if Registry.ValueExists('PNGTransparency') then begin
         PNGTransparency := Registry.ReadInteger('PNGTransparency');
@@ -675,6 +681,7 @@ begin
 //      ResizeOnLoad := False;
       ShowProgress := true;
       SaveIncompleteRenders := false;
+      LowerRenderPriority := false;
       ShowRenderStats := false;
       PNGTransparency := 1;
       ShowTransparency := False;
@@ -1132,6 +1139,7 @@ begin
 
       Registry.WriteBool('SaveIncompleteRenders', SaveIncompleteRenders);
       Registry.WriteBool('ShowRenderStats', ShowRenderStats);
+      Registry.WriteBool('LowerRenderPriority', LowerRenderPriority);
 
       Registry.WriteInteger('NrTreads', NrTreads);
       Registry.WriteInteger('UseNrThreads', UseNrThreads);
diff --git a/2.10/Source/Render.pas b/2.10/Source/Render.pas
index aeacdcd..b9fa265 100644
--- a/2.10/Source/Render.pas
+++ b/2.10/Source/Render.pas
@@ -66,6 +66,7 @@ type
     FCompatibility: integer;
     FNumThreads: integer;
     FNumBatches: integer;//int64;
+    FThreadPriority: TThreadPriority;
 
     FMinDensity: double;
     FMinBatches: integer;
@@ -112,6 +113,7 @@ type
     procedure BreakRender; virtual;
     procedure Pause; virtual;
     procedure UnPause; virtual;
+    procedure SetThreadPriority(p: TThreadPriority); virtual;
 
     function Failed: boolean;
 
@@ -187,6 +189,7 @@ begin
   FNumSlices := 1;
   FSlice := 0;
   FStop := 0; // False;
+  FThreadPriority := tpNormal;
 
   FImageMaker := TImageMaker.Create;
 end;
@@ -242,6 +245,11 @@ begin
   TimeTrace('Resuming render');
 end;
 
+procedure TBaseRenderer.SetThreadPriority(p: TThreadPriority);
+begin
+  FThreadPriority := p;
+end;
+
 ///////////////////////////////////////////////////////////////////////////////
 procedure TBaseRenderer.Stop;
 begin
@@ -311,7 +319,7 @@ begin
     strOutput.Add(Format('  Max Count: %2.3f bits', [Abits]));
     strOutput.Add(Format('  Point hit ratio: %2.2f%%', [100.0*(TotalA/TotalSamples)]));
     if RenderTime > 0 then // hmm
-      strOutput.Add(Format('  Average speed: %n points per second', [TotalSamples / (RenderTime * 24 * 60 * 60)]));
+      strOutput.Add(Format('  Average speed: %n iterations per second', [TotalSamples / (RenderTime * 24 * 60 * 60)]));
     strOutput.Add('  Pure rendering time:' + TimeToString(RenderTime));
   end;
 end;
@@ -324,7 +332,7 @@ begin
 
   TotalSamples := int64(FNumBatches) * SUB_BATCH_SIZE; // * fcp.nbatches ?
   if RenderTime > 0 then // hmm
-    strOutput.Add(Format('  Average speed: %n points per second', [TotalSamples / (RenderTime * 24 * 60 * 60)]));
+    strOutput.Add(Format('  Average speed: %n iterations per second', [TotalSamples / (RenderTime * 24 * 60 * 60)]));
   strOutput.Add('  Pure rendering time:' + TimeToString(RenderTime));
 end;
 
diff --git a/2.10/Source/RenderMT.pas b/2.10/Source/RenderMT.pas
index 2f6a1ed..d2d8e56 100644
--- a/2.10/Source/RenderMT.pas
+++ b/2.10/Source/RenderMT.pas
@@ -49,6 +49,7 @@ type
 
     procedure Pause; override;
     procedure UnPause; override;
+    procedure SetThreadPriority(p: TThreadPriority); override;
 
   end;
 
@@ -96,9 +97,9 @@ begin
 
       Progress(batchcounter / FNumBatches);
       bc := batchcounter;
-     finally
-       LeaveCriticalSection(CriticalSection);
-     end;
+    finally
+      LeaveCriticalSection(CriticalSection);
+    end;
   end;
 
   for i := 0 to High(WorkingThreads) do begin
@@ -165,11 +166,22 @@ begin
     WorkingThreads[i].Resume;
 end;
 
+procedure TBaseMTRenderer.SetThreadPriority(p: TThreadPriority);
+var
+  i: integer;
+begin
+  inherited;
+  
+  for i := 0 to High(WorkingThreads) do
+    WorkingThreads[i].Priority := p;
+end;
+
 ///////////////////////////////////////////////////////////////////////////////
 function TBaseMTRenderer.NewThread: TBucketFillerThread;
 begin
   Result := TBucketFillerThread.Create(fcp);
   assert(Result<>nil);
+  Result.Priority := FThreadPriority;
 
   if FCP.FAngle = 0 then
     Result.AddPointsProc := self.AddPointsToBuckets
diff --git a/2.10/Source/RenderThread.pas b/2.10/Source/RenderThread.pas
index e426a1c..4f4c272 100644
--- a/2.10/Source/RenderThread.pas
+++ b/2.10/Source/RenderThread.pas
@@ -73,6 +73,7 @@ type
     procedure Suspend;
     procedure Resume;
     procedure BreakRender;
+    procedure SetPriority(p: TThreadPriority);
 
 //    procedure GetBucketStats(var Stats: TBucketStats);
     procedure ShowBigStats;
@@ -203,6 +204,7 @@ begin
   end;
 
   FRenderer.SetCP(FCP);
+  FRenderer.SetThreadPriority(self.Priority);
 //  FRenderer.compatibility := compatibility;
   FRenderer.MinDensity := FMinDensity;
   FRenderer.OnProgress := FOnProgress;
@@ -275,6 +277,14 @@ begin
     FRenderer.BreakRender;
 end;
 
+procedure TRenderThread.SetPriority(p: TThreadPriority);
+begin
+  Priority := p;
+
+  if assigned(FRenderer) then
+    FRenderer.SetThreadPriority(p);
+end;
+
 ///////////////////////////////////////////////////////////////////////////////
 function TRenderThread.GetNrSlices: integer;
 begin