Are you sure you're not referring to this? http://www.wolframalpha.com/input/?i=56+Kbps+in+KB%2Fs http://www.wolframalpha.com/input/?i=56+Kbps+in+KB%2Fs With

Are you sure you're not referring to this? http://www.wolframalpha.com/input/?i=56+Kbps+in+KB%2Fs http://www.wolframalpha.com/input/?i=56+Kbps+in+KB%2Fs With 8 bits per byte plus protocol overhead, a good rule of thumb is take the Kbps value and divide by 10 to get a realistic KB/s figure. It's been too long since the BBS/dialup days and I don't recall if some of the later modems implemented on-the-fly compression which would squeeze out even more bandwidth.