Well, as mentioned in my initial post - it's not an alternative using adapters. My boss tells me, although I'm not sure it's true, that adapters arent accurate enough.
So I really need to find a high performance laptop with serial integrated.
From the web somewhere:
"But if you've got something more esoteric, with tight timing
requirements, such as a chip programmer or a dongle, something that
isn't "pure", it may be that no USB device will work with it. For
example, no USB serial or parallel port (that I'm aware of, at least)
will allow you to toggle a control line faster than 500 Hz (the time
base for USB frames is 1 ms).
The newest notebook I've seen that's also powerful is actually my Sager NP5793. I've only used that port once to manage some old switch. You can probably find a used one, but they really don't make them anymore..
We have the same problem an adapter cannot keep up with small packet data in a high frequency stream, it simply cannot make the analog digital conversion fast enough and fails within a minute of running have tried 20 different ones. HP Probook 6550b are what we are now using has serial port i7 processor and is actually a really solid laptop. I keep trying to let HP know that the only reason I buy them is for the serial port so hopefully they continue with it on at least one model I now have 30 of these laptops so should be reason enough for them to continue. Good luck