Path: utzoo!utgpu!news-server.csri.toronto.edu!rpi!zaphod.mps.ohio-state.edu!cis.ohio-state.edu!tut.cis.ohio-state.edu!VAX1.CC.UAKRON.EDU!neoucom.edu!wtm From: wtm@uhura.neoucom.EDU (Bill Mayhew) Newsgroups: comp.dcom.modems Subject: Re: T1000 and 2400 baud vs. 9600 for interactive use Message-ID: <1991May14.022334.10752@uhura.neoucom.EDU> Date: 14 May 91 02:23:34 GMT References: <64136@bbn.BBN.COM> Organization: Northeastern Ohio Universities College of Medicine Lines: 33 On a slightly related note, I usually use T1000 and TB+ modems in V.22bis mode as opposed to PEP mode for interactive typing connections. The TB modems with newer firmware use an input buffer low-water mark sensing strategy that allows the modems to switch to shorter packets as the input buffer empties. The short packets are 40 mS long, while the standard packes are 136 mS. This mode switching is noticable when catting a file: you'll see the first few lines dump to your screen at a liesurely pace, followed by a brief pause, then a torrent of output. The problem is that PEP mode is half-duplex, which means that echoing a typed character in interactive mode takes about 80 mS plus change and host / client overheads. This corresponds to only about 12 character per second typing. While the TB has an input buffer, the result is annoyingly choppy display of the characters. Thought a ^L screen repaint in vi takes several seconds longer at 2400 bps, the usability factor with 240 cps bidirectional link makes interactive use limitlessly smoother and more satisfying. V.42 modems seem to exhibit similar choppieness for interactive typing while they consider whether or not to buffer characters for compression. I use an AT sequence in my cu dialer string to make sure V.42 compression is switched off when using a V.32 modem. Now, if manufacturers would only standardize the AT sequence! Bill -- Bill Mayhew NEOUCOM Computer Services Department Rootstown, OH 44272-9995 USA phone: 216-325-2511 wtm@uhura.neoucom.edu ....!uunet!aablue!neoucom!wtm via internet: (140.220.001.001)