diff --git a/delphi/TESTMAIN.PAS b/delphi/TESTMAIN.PAS
index 1f35e13..65e6ecb 100644
--- a/delphi/TESTMAIN.PAS
+++ b/delphi/TESTMAIN.PAS
@@ -165,13 +165,18 @@ end;
 
 
 procedure TMainForm.Run;
+const
+  RenderMs = 50;   { Minimum ms between renders during bulk flow (20 fps) }
 var
-  Msg:     TMsg;
-  S:       string;
-  HasData: Boolean;
+  Msg:            TMsg;
+  S:              string;
+  HasData:        Boolean;
+  Now:            Longint;
+  LastRenderTick: Longint;
 begin
   Show;
-  FDone := False;
+  FDone          := False;
+  LastRenderTick := GetTickCount;
   while not FDone do
   begin
     { Process all pending Windows messages (keyboard, paint, scrollbar) }
@@ -218,9 +223,16 @@ begin
     if FDone then
       Break;
 
-    { Tick blink (dirties rows if interval elapsed), then render }
-    FAnsi.TickBlink;
-    FAnsi.FlipToScreen;
+    { Render throttle: during bulk data flow, only render every RenderMs }
+    { to decouple parse throughput from GDI overhead.  When idle, render  }
+    { immediately for interactive responsiveness.                         }
+    Now := GetTickCount;
+    if (not HasData) or (Now - LastRenderTick >= RenderMs) then
+    begin
+      FAnsi.TickBlink;
+      FAnsi.FlipToScreen;
+      LastRenderTick := Now;
+    end;
 
     { Yield CPU to other apps when no serial data is flowing.          }
     { PM_NOYIELD keeps message draining fast; Yield here gives other   }