BiModem
BiModem is a new communications protocol which allows simultaneous bidirectional file transfers. Yes, BiModem can upload while downloading. Imagine the time savings if you could upload with Zmodem (tm) and YmodemG efficiencies while downloading at the same efficiency at the same time. The applications for such a protocol are many, and I will not try to cover them here. Everyone from occasional BBS users to full time network managers will appreciate the advantages of exploiting full duplex operations. Even for those with small and moderate volumes of data to transfer, the time savings can be very significant. Please do not expect a 50% decrease in your overall modem transfer time. This can only be achieved when the same amount of information is transmitted in both directions, and does not account for the overhead of specifying the lists of files to download and upload.
Performance
We wanted a fair way to compare BiModem and other protocols... so what we did was download 6 files using each of 3 transfer protocols. We chose Telink which was about as close to XMODEM as we could get and still support wildcard downloads, Zmodem which is very popular these days, and BiModem. We timed the execution from the time we pressed enter to start the transfer until the system responded ready to enter more commands. The tests were conducted using a 1200 baud modem connection from an 8mhz XT compatible to a 10mhz AT compatible which was running the BBS software (OPUS v1.03b). The XT was using Telix version 3.10. Here are our results:
Downloading 6 2136 byte files:
Telink - 2 minutes 45 seconds
Zmodem - 2 minutes 29 seconds
BiModem- 2 minutes 07 seconds
Downloading 6 2136 byte files and uploading 6 2136 byte files
Telink - 5 minutes 30 seconds
Zmodem - 4 minutes 58 seconds
BiModem- 2 minutes 07 seconds