diff --git a/floppy.cs b/floppy.cs
index a10a8f6..4ceebf8 100644
--- a/floppy.cs
+++ b/floppy.cs
@@ -16,6 +16,7 @@ class FloppyDisk : Device
     private int [] _cylinder = new int[4];
     private int [] _head = new int[4];
     private int _cylinder_seek_result = 0;
+    private static readonly System.Threading.Lock _filenames_lock = new();
 
     public FloppyDisk(List<string> filenames)
     {
@@ -23,6 +24,38 @@ public FloppyDisk(List<string> filenames)
         _filenames = filenames;
     }
 
+    public int GetUnitCount()
+    {
+        return _filenames.Count();
+    }
+
+    public string GetUnitFilename(int unit)
+    {
+        lock(_filenames_lock)
+        {
+            if (unit < _filenames.Count())
+            {
+                return _filenames[unit];
+            }
+        }
+
+        return null;
+    }
+
+    public bool SetUnitFilename(int unit, string filename)
+    {
+        lock(_filenames_lock)
+        {
+            if (unit < _filenames.Count())
+            {
+                _filenames[unit] = filename;
+                return true;
+            }
+        }
+
+        return false;
+    }
+
     public override int GetIRQNumber()
     {
         return _irq_nr;
@@ -123,29 +156,33 @@ public override (byte, bool) IO_Read(ushort port)
 
     private byte [] GetFromFloppyImage(int unit, int cylinder, int head, int sector, int n)
     {
-        long file_size = new System.IO.FileInfo(_filenames[unit]).Length;
-        int sectors_per_track = 9;
-        if (file_size >= 819200)
-            sectors_per_track = 18;
-
-        if (sector > sectors_per_track)
-            Log.DoLog($"Floppy-ReadData: reading beyond sector-count? ({sector} > {sectors_per_track})");
-
         byte[] b = new byte[256 * n];
-        int lba = (cylinder * 2 + head) * sectors_per_track + sector - 1;
-        long offset = lba * b.Length;
-        Log.DoLog($"Floppy-ReadData LBA {lba}, offset {offset}, n {n} C {cylinder} H {head} S {sector} ({sectors_per_track})", true);
 
-        for(int nr=0; nr<n; nr++)
+        lock(_filenames_lock)
         {
-            using (FileStream fs = File.Open(_filenames[unit], FileMode.Open, FileAccess.Read, FileShare.None))
+            long file_size = new System.IO.FileInfo(_filenames[unit]).Length;
+            int sectors_per_track = 9;
+            if (file_size >= 819200)
+                sectors_per_track = 18;
+
+            if (sector > sectors_per_track)
+                Log.DoLog($"Floppy-ReadData: reading beyond sector-count? ({sector} > {sectors_per_track})");
+
+            int lba = (cylinder * 2 + head) * sectors_per_track + sector - 1;
+            long offset = lba * b.Length;
+            Log.DoLog($"Floppy-ReadData LBA {lba}, offset {offset}, n {n} C {cylinder} H {head} S {sector} ({sectors_per_track})", true);
+
+            for(int nr=0; nr<n; nr++)
             {
-                fs.Seek(offset, SeekOrigin.Begin);
-                if (fs.Read(b, 256 * nr, 256) != 256)
-                    Log.DoLog($"Floppy-ReadData failed reading from backend ({_filenames[unit]}, offset: {offset})", true);
-                if (fs.Position != offset + 256)
-                    Log.DoLog($"Floppy-ReadData backend data processing error?", true);
-                offset += 256;
+                using (FileStream fs = File.Open(_filenames[unit], FileMode.Open, FileAccess.Read, FileShare.None))
+                {
+                    fs.Seek(offset, SeekOrigin.Begin);
+                    if (fs.Read(b, 256 * nr, 256) != 256)
+                        Log.DoLog($"Floppy-ReadData failed reading from backend ({_filenames[unit]}, offset: {offset})", true);
+                    if (fs.Position != offset + 256)
+                        Log.DoLog($"Floppy-ReadData backend data processing error?", true);
+                    offset += 256;
+                }
             }
         }
 
@@ -154,8 +191,11 @@ private byte [] GetFromFloppyImage(int unit, int cylinder, int head, int sector,
 
     private bool ReadData(int unit)
     {
-        if (unit >= _filenames.Count())
-            return false;
+        lock(_filenames_lock)
+        {
+            if (unit >= _filenames.Count())
+                return false;
+        }
 
         int sector = _data[4];
         int head = (_data[1] & 4) == 4 ? 1 : 0;
diff --git a/main.cs b/main.cs
index f200ebb..71249ff 100644
--- a/main.cs
+++ b/main.cs
@@ -216,8 +216,7 @@
             Console.Write("==>");
 
         string line = Console.ReadLine();
-
-        //Log.DoLog(line);
+        Log.DoLog(line, true);
 
         string[] parts = line.Split(' ');
 
@@ -399,9 +398,7 @@
         {
             p.ResetCrashCounter();
 
-            while(p.Tick())
-            {
-            }
+            runner(p);
         }
         else if (line != "")
         {
@@ -413,6 +410,49 @@
 }
 else
 {
+    Thread thread = new Thread(runner);
+    thread.Name = "runner";
+    thread.Start(p);
+
+    for(;;)
+    {
+        Console.Write("==>");
+
+        string line = Console.ReadLine();
+        Log.DoLog(line, true);
+        if (line == "")
+            continue;
+
+        if (line == "quit")
+            break;
+
+        if (line == "help")
+        {
+            Console.WriteLine("quit           terminate application");
+//            Console.WriteLine("lsfloppy       list configured floppies");
+ //           Console.WriteLine("setfloppy x y  set floppy unit x (0 based) to file y");
+        }
+  //      else if (line == "lsfloppy")
+   //     {
+    //    }
+        else
+        {
+            Console.WriteLine($"\"{line}\" is not understood");
+        }
+    }
+}
+
+Log.EmitDisassembly();
+    
+if (test != "" && mode == TMode.Binary)
+    System.Environment.Exit(p.GetSI() == 0xa5ee ? 123 : 0);
+
+System.Environment.Exit(0);
+
+void runner(object p_in)
+{
+    P8086 p = (P8086)p_in;
+
     try
     {
         long prev_time = DateTime.Now.Ticks / TimeSpan.TicksPerMillisecond;
@@ -441,10 +481,3 @@
         Log.DoLog(msg);
     }
 }
-
-Log.EmitDisassembly();
-    
-if (test != "" && mode == TMode.Binary)
-    System.Environment.Exit(p.GetSI() == 0xa5ee ? 123 : 0);
-
-System.Environment.Exit(0);