Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Path: utzoo!utgpu!water!watmath!clyde!ho95e!wcs From: wcs@ho95e.UUCP Newsgroups: comp.sources.d,comp.terminals Subject: Re: VT100's keeping up at high baud rates Message-ID: <1490@ho95e.ATT.COM> Date: Tue, 16-Jun-87 18:16:22 EDT Article-I.D.: ho95e.1490 Posted: Tue Jun 16 18:16:22 1987 Date-Received: Thu, 18-Jun-87 01:40:33 EDT References: <1149@carthage.swatsun.UUCP> <8601@tekecs.TEK.COM> <6828@mimsy.UUCP> <1075@laidbak.UUCP> <1119@copper.TEK.COM> Reply-To: wcs@ho95e.UUCP (46133-Bill.Stewart,2G218,x0705,) Organization: AT&T Bell Labs 46133, Holmdel, NJ Lines: 36 Xref: utgpu comp.sources.d:791 comp.terminals:283 In article <1119@copper.TEK.COM> stevesu@copper.TEK.COM (Steve Summit) writes: >> - Some (all?) PC/clones cannot keep up with speeds > 4800 baud in the VT100 >> - terminal emulator >> >> It sounds as if you're suggesting that any AT&T terminal will keep up at >> speeds greater than 4800 baud! I have news for you: not all of them do. There are two real issues here - how fast can a terminal go with flow control enabled, and how fast can it go with flow control disabled. While it's nice to have a terminal that can keep up with 19200 without flow control (i.e. continuous text display), that's approximately 19200 words per minute, and neither you nor I nor Evelyn Wood's mother can read that fast over sustained periods. The reasons you'd want a terminal to go that fast without flow control are either that you use a braindamaged computer which can't handle it, or that you're using EMACS, and flow control ^S puts you into search mode. (The solution there is to fix the software.) As far as keeping up without losing characters, the PC's serial I/O capability is pretty limited - you have to program well to make it go fast at all. A couple years ago (when we got Datakit 19200 baud capability), I benchmarked whatever terminals were aound to see whether to use 19200 or 9600. time cat /etc/termcap followed by some arithmetic. My 5420 (predecessor to the 5425, 610, etc.) did about 8300 baud at 9600 and 8600 at 19.2. My 5620 (with the old firmware) got about 6600 baud, and 2600 in layers. I'm since using better layers software, but I don't really know how fast it is. We cranked an HP terminal to about 12000 baud. One commentator here questioned the sanity of putting microprocessors in terminals at all. I'm all in favor of it - assuming you provide decent programming hooks, you allow the user to build a decent terminal environment. An 80186 and 128K RAM shouldn't cost you more than $50, but that lets you build windows, downloadable fonts, etc., and allows the user to undo any mistakes in the original firmware. -- # Bill Stewart, AT&T Bell Labs 2G-202, Holmdel NJ 1-201-949-0705 ihnp4!ho95c!wcs