diff --git a/README.md b/README.md
index b70b97d..c603b48 100644
--- a/README.md
+++ b/README.md
@@ -232,8 +232,6 @@ tek4010 has the following options:
 
 **Reporting problems**
 
-As this software is still in beta test, there will be problems.
-
 If everything works properly for you, but your graphics application produces garbage on the
 tek4010 emulator, you can send me your data as follows: On a historical Unix system, type
 
@@ -259,7 +257,7 @@ module.
 If called with the -full option, the tek4010 emulator creates creates a full screen window,
 and uses the full 4K resolution of the 4014 with enhanced graphics
 module installed, scaled down to the actual window size.
-Use control-q to close the tek4010 window. This option is experimental.
+Use control-q to close the tek4010 window.
 
 **Compiling the tek4010 project**
 
@@ -269,6 +267,15 @@ If you want to compile the project, you need to install "libgtk-3-dev":
 
 There is a make file in the repo.
 
+**Using tek4010 on OSX and Windows using VirtualBox and Ubuntu**
+
+It is possible to run tek4010 in a virtual Ubuntu environment on OSX or Windows. I found that in
+such virtual environments the raw CPU speed is usually higher than on a Raspberry Pi, but the
+actual frame rates are sometimes slower. I have made a substantial effort to make sure that the bright
+spot animations also look good in environments with rather slow frame rates, but do not expect a
+miracle. Emulating a storage tube display without any screen refresh requirements on a machine
+with limited frame rate has its limitations.
+
 **Version**
 
 See [versions.txt](versions.txt)
diff --git a/main.c b/main.c
index 23d2b7f..da15b86 100644
--- a/main.c
+++ b/main.c
@@ -34,7 +34,7 @@
  * 
  */
  
-#define TIME_INTERVAL       5              // time interval for timer function in msec (after last refresh)
+#define TIME_INTERVAL       35              // time interval for timer function in msec (after last refresh)
  
 #define GDK_DISABLE_DEPRECATION_WARNINGS
 
diff --git a/tek4010 b/tek4010
index 413135c..feb5c9f 100755
Binary files a/tek4010 and b/tek4010 differ
diff --git a/tek4010.c b/tek4010.c
index 25c43ab..aa34fdc 100755
--- a/tek4010.c
+++ b/tek4010.c
@@ -26,7 +26,7 @@
  
 #define DEBUG    0              // print debug info
  
-#define TODO  (long)(8.0 * efactor * efactor)   // draw multiple objects until screen updates
+#define TODO  (long)(16)   // draw multiple objects until screen updates
 
 #define _GNU_SOURCE
  
diff --git a/tube.c b/tube.c
index 795ea77..d3384f2 100755
--- a/tube.c
+++ b/tube.c
@@ -178,7 +178,7 @@ void tube_init(int argc, char* argv[])
         char *argv2[20];
         size_t bufsize = 127;
         int firstArg = 1;
-        printf("tek4010 version 1.2.3\n");
+        printf("tek4010 version 1.2.4\n");
         windowName = "Tektronix 4010/4014 emulator";
         if ((argc<2) || (argc>19)) {
                 printf("Error:number of arguments\n");
diff --git a/versions.txt b/versions.txt
index c0d4ad3..ca73e37 100644
--- a/versions.txt
+++ b/versions.txt
@@ -1,3 +1,9 @@
+Version 1.2.4 April 18, 2019
+============================
+Bug fixes
+- Optimized for a variety of displays, cpu speeds and actual frame rates, including
+  VirtualBox environments
+
 Version 1.2.3 April 17, 2019
 ============================
 Bug fixes