Check out these links and see if they help. Please let me know if they do not fully address your concerns:

http://www.empirisoft.com/Support/showthread.php?t=71
http://www.empirisoft.com/Support/showthread.php?t=256
http://www.empirisoft.com/Support/showthread.php?t=55
http://www.empirisoft.com/Support/showthread.php?t=1003

Ultimately, if you want to know exactly, and without doubt, what display times you are actually getting, you can test any display software with an oscilloscope. However, if serves for any immediate comfort, DirectRT was developed primarily on computers and laptops with LCD displays.