sr16+@andrew.cmu.edu (Seth Benjamin Rothenberg) (10/05/89)
We are going to be getting a UNIX machine soon, probably a DEC 5800. We are considering how terminals should be connected to it. We were told that character input from hardwired terminals (as opposed to virtual terminals) causes cpu interrupts. Is this true? Would this slow the machine down a great deal? On our TI 990, our user systems all use 'octacom' boards to handle line-editing; only complete lines and control chars get sent to the cpu. Most of the systems I know of use telnet (or LAT) logins almost exclusively. Are hardwired terminals just as efficient? One factor is that we have abot 100 terminals installed already, so hardwiring would be easy, but we expect to double that soon, so moving to ethernet would make that expansion easier. Any comments, suggestions are appreciated. BTW, if we go to ethernet, should we leave the existing wiring in place in case of an "emergency"? Thanks Seth Rothenberg sr16@andrew.cmu.edu
gwyn@smoke.BRL.MIL (Doug Gwyn) (10/05/89)
In article <wZ_XRne00WB4I4M4kT@andrew.cmu.edu> sr16+@andrew.cmu.edu (Seth Benjamin Rothenberg) writes: >We were told that character input from hardwired terminals (as opposed to >virtual terminals) causes cpu interrupts. Is this true? Would this >slow the machine down a great deal? It depends on the serial line multiplexer and the operating system. Most commonly encountered VAX serial line multiplexers are used by most common UNIX implementations in a single interrupt per character mode. (There are exceptions, generally involving I/O processors.) It's not a large problem for typical installations. >Most of the systems I know of use telnet (or LAT) logins almost exclusively. >Are hardwired terminals just as efficient? The main advantage of Ethernet access is that, until the net gets saturated, you can sustain higher throughput. Most RS-232 terminals cannot communicate faster than 19,200 bps. >BTW, if we go to ethernet, should we leave the existing wiring >in place in case of an "emergency"? I wouldn't think it would help. If your Ethernet stops working, it would be less work to fix it than to convert from an Ethernet base to an RS-232 one.
davidsen@crdos1.crd.ge.COM (Wm E Davidsen Jr) (10/05/89)
Since you have the serial lines in place already, and the terminals, why not use a serial to ethernet bridge to put all of your terminals "on ethernet" as far as the computer is concerned? Just a thought, we run some direct lines and some through bridges. -- bill davidsen (davidsen@crdos1.crd.GE.COM -or- uunet!crdgw1!crdos1!davidsen) "The world is filled with fools. They blindly follow their so-called 'reason' in the face of the church and common sense. Any fool can see that the world is flat!" - anon
samlb@pioneer.arc.nasa.gov (Sam Bassett RCD) (10/08/89)
In article <wZ_XRne00WB4I4M4kT@andrew.cmu.edu> sr16+@andrew.cmu.edu (Seth Benjamin Rothenberg) writes: >We >were told that character input from hardwired terminals (as opposed to >virtual terminals) causes cpu interrupts. Is this true? This very much depends on the design of the serial interface board in your DEC machine -- some do, and some don't. Pioneer is an ancient VAX 11/785, and we swapped out some interrupt-on-character serial boards, and speeded up the system something fierce. What you need to do is hold the DEC salesperson's feet to the fire about the serial boards -- if you have a DEC C.E. around handy, ask him/her/it which boards do & don't cause keystroke interrupts. BTW -- we have quite a few Annex boxes from Encore around here, which take up to 32 serial lines and put them on the Ethernet -- as I understand it, they cost in the high 5 to low 6 digits -- very convenient. Sam'l Bassett, Sterling Software @ NASA Ames Research Center, Moffett Field CA 94035 Work: (415) 694-4792; Home: (415) 969-2644 samlb@well.sf.ca.us samlb@ames.arc.nasa.gov <Disclaimer> := 'Sterling doesn't _have_ opinions -- much less NASA!'
karish@forel.stanford.edu (Chuck Karish) (10/08/89)
In article <3365@amelia.nas.nasa.gov> samlb@pioneer.arc.nasa.gov (Sam Bassett RCD) wrote: > BTW -- we have quite a few Annex boxes from Encore around here, >which take up to 32 serial lines and put them on the Ethernet -- as I >understand it, they cost in the high 5 to low 6 digits -- very >convenient. They don't cost that much. The last I heard (three years ago) a Bridge 14-port box cost between $4000 and $5000 (educational institution; not as big a discount as DEC offers). The per-port cost should be less for a bigger server. Chuck Karish karish@mindcraft.com (415) 493-9000 karish@forel.stanford.edu