tgm@ecl.psu.edu (03/02/91)
In article <7061@mentor.cc.purdue.edu>, lingerke@mentor.cc.purdue.edu (Ken Linger) writes: > When I am downloading something from Unix with Zterm, the best I can get with > my 2400 baud modem is 21% efficiency. Is there a way to improve this? Zterm calculates efficiency by comparing the speed of data during the download with that of the current modem (or printer) port setting--not the speed at which your modem works. If your port setting is higher than your modem's actual speed, your efficiency will look low. For example, if you modem port is set to 9600 and you connect with a system at 2400 then your maximum efficieny will be 2400/9600 = 25%, assuming your modem does not use any data compression. A better way to judge efficiency with Zterm is use the chars per second measurement. With a 2400 baud modem an approximation of your theoretical maximum chars/sec is (2400)/(10) = 240 cps, where 10 is the number of bits per transmitted char (i.e., 8 data + 1 start + 1 stop). If you're getting cps ratings of around 240, then don't worry; everything is fine. But if 50 cps is what your getting, then the 21% efficiency figure is correct and something is probably wrong. In that case you might want want to try the following: (1) Use the -e option. This tells sz to pass all control characters in a ``safe'' format that does't conflict with any devices between the Un!x system and your Mac. (2) Don't forget the -b if you're transmitting binary (data) files. (Not needed with .hqx files) If those doesn't work, try this method (it worked for me!): (3) Use the -w option to set the xfer window size to a small value, 512 (or 256). This makes sure that the Un!x end never gets more than 512 chars ahead of your Mac, preventing data from being lost by buffer overwrites in the communications channel. This might cause a slight loss of performance, so if 512 works, experiment with larger values, which are more efficient (4096 is default) Here's the command I use to tranfer files under hellish conditions: sz -e -b -w 512 files... Hope this helps. --Tom Moertel thor@chopin.psu.edu