Xref: utzoo comp.sys.ibm.pc.misc:10552 comp.dcom.modems:10473 Path: utzoo!utgpu!news-server.csri.toronto.edu!bonnie.concordia.ca!thunder.mcrcim.mcgill.edu!snorkelwacker.mit.edu!usc!elroy.jpl.nasa.gov!swrinde!mips!spool.mu.edu!uunet!hayes!tnixon From: tnixon@hayes.uucp Newsgroups: comp.sys.ibm.pc.misc,comp.dcom.modems Subject: Re: 4.77MHz PC sufficient for 19200 bps modem? Message-ID: <4028.285f4e1e@hayes.uucp> Date: 19 Jun 91 12:29:17 GMT References: <1991Jun18.201125.6198@cs.cmu.edu> Organization: Hayes Microcomputer Products, Norcross, GA Lines: 39 In article <1991Jun18.201125.6198@cs.cmu.edu>, jch+@cs.cmu.edu (Jonathan Hardwick) writes: > A housemate has an original Big Blue IBM PC, running at the blazing > speed of 4.77MHz. We want to use this as a dumb terminal to access > our university workstations. The university offers 2400 bps service > with MNP level 5, and a 9600 bps or 19200 bps MCN service using DOV > modems. We'd really like the extra speed if possible. Is the PC > going to be able to keep up with 19200 bps? How about 9600 bps? Before coming to Hayes, I worked for Datamaxx USA Corp, writing firmware for terminal emulators. Their biggest-selling product was based on a Motorola 6800 processor running at 1 MHz, and supported up to 9600bps -- without flow control, and without ever losing data! So, I _know_ that a 4.77MHz processor _can_ support 9600, even 19200, _if_ your comm software is well written. That's the real trick: finding a program that is efficiently written, properly supports flow control, scrolls fast, properly schedules writes to disk to avoid slowdowns, etc. Hayes Smartcom Exec is one such program (its what I use), but I'm sure you can get plenty of recommendations for good programs that can keep up with 9600 or 19200 on a 4.77 MHz PC. If you're doing anything fancy on the PC (running TSRs that hook into the timer interrupt, or a LAN card, or RAMdisk), then you may want to invest in a buffered serial port card like Hayes ESP. This provides 1024 bytes of buffer in the hardware, plus automatic hardware flow control, so even if the main CPU gets a bit behind tending to other things, you still don't lose characters. It's a lot cheaper and easier than getting a new motherboard, assuming you're using a modem that has flow control. So, anyway, my advice is, "go for it". -- Toby Nixon, Principal Engineer | Voice +1-404-840-9200 Telex 151243420 Hayes Microcomputer Products Inc. | Fax +1-404-447-0178 CIS 70271,404 P.O. Box 105203 | UUCP uunet!hayes!tnixon AT&T !tnixon Atlanta, Georgia 30348 USA | Internet hayes!tnixon@uunet.uu.net