Do these i/o interfaces tell you their expected latency and throughput numbers? I could see some fairly silly code being written because they didn't realize that file was actually a a bad cell phone connection.
I actually had Plan 9 working on some Sun 3/50s at one point. You could use it over a 2400 baud modem... a kind of broken one where I had to listen to the connection noises and twiddle the wires at the right moment to make it connect. A bad cell phone connection would have been nice.