tidedu@mars.lerc.nasa.gov (William T. Dedula) (10/15/90)
Hello All; I am currently evaluating low cost, easily implemented methods of connecting 6 or 7 IBM PC-XT/AT's in a Local Area Network. I am about to begin to develop educational/simulation software which will operate independently on each PC but will have the capability of communicating with the other PC's in the network. I have heard that it is possible to utilize RS-232 serial ports on each computer to implement the network. If anyone has heard of (Or done) this, I'd be interested in knowing the BEST, and MOST EFFICIENT way this can be done. I would particularly be interested in how the serial ports could be connected together but will certaintly welcome any other information you may have about this method. Thank you very much !!! Tim Dedula ---------------------------------------------------------------- W. Tim Dedula Internet: N.A.S.A. Lewis Research Center tdedula@nasamail.nasa.gov Mail Stop 77-3 tidedu@mars.lerc.nasa.gov 21000 BrookPark Road aa252@cleveland.freenet.edu Cleveland, Ohio 44135 Phone (216) 433-3668 The National Aeronautics and Space Administration: Science and Technology ... for the Benefit of ALL Mankind !!!
fyl@ssc.UUCP (Phil Hughes) (10/23/90)
In article <1990Oct15.030111.28548@eagle.lerc.nasa.gov>, tidedu@mars.lerc.nasa.gov (William T. Dedula) writes: > I am currently evaluating low cost, easily implemented methods > of connecting 6 or 7 IBM PC-XT/AT's in a Local Area Network. > I am about to begin to develop educational/simulation software > which will operate independently on each PC but will have the > capability of communicating with the other PC's in the network. > I have heard that it is possible to utilize RS-232 serial ports > on each computer to implement the network. If anyone has heard > of (Or done) this, I'd be interested in knowing the BEST, and > MOST EFFICIENT way this can be done. For small networks (2 or 3 machines) a really inexpensive solution that seems to work well is called the $25 Network. I am not a DOS fan but bought it just to see if it works. It does. For the $25 you get the software and license to run the complete network. I hooked up a Toshiba T1000 to a 386SX system to test it out. Access to the disk on the 386 from the Toshiba worked fine (as did the other way around) and remote print is also supported. Various utility routines come with the network. The one that I use is a program that fakes out Windows to think that there really is a printer on LPT3 (which is really just a way to send data to UltraScript). That program alone was worth the $25. The product is available from: Information Modes P.O. Drawer F Denton, TX 76202 (817) 387-3339 I ordered mine by phone and it showed up about two days later. -- Phil Hughes, SSC, Inc. P.O. Box 55549, Seattle, WA 98155 (206)FOR-UNIX uunet!pilchuck!ssc!fyl or attmail!ssc!fyl (206)527-3385
imp@jhereg.osa.com (Charles T. Lukaszewski) (10/25/90)
In article <1990Oct15.030111.28548@eagle.lerc.nasa.gov> tidedu@ mars.lerc.nasa.gov writes: >I have heard that it is possible to utilize RS-232 serial ports >on each computer to implement the network. If anyone has heard >of (Or done) this, I'd be interested in knowing the BEST, and >MOST EFFICIENT way this can be done. I would particularly be If this is really the method you wish to use, there are a number of imple- mentations of this style of network, which fall into two categories. The first category would be standalone systems like the system from Newbridge Networks which use concentrators and home runs in a star-like topology. (There are many others - I'm not endorsing Newbridge per se). The second method is to use a private branch exchange (PBX) that is capable of switching between RS-232 devices. I know that Rolm has such a beast, and that Northern Telecom used to have something like this. Again, others can probably provide more specifics, but these are the basic routes. In my opinion, RS-232 based networks are more cumbersome than helpful. By definition, your throughput will be at least several tens (Arcnet) to several hundreds (Ethernet) of times slower. Also, it is arguable whether the one-user-at-a-time limit isn't any worse than Ethernet. You might at least cost-compare building an Ethernet or Token-Ring network with a non-server based Network Operating System like Tops. -- _______________________________________________________________________________ Charles T. Lukaszewski imp@osa.com 612 525-0000 Managing Partner & Chairman Open Systems Architects, Inc. "Who needs a disclaimer? I liked the opinions so much, I bought the company!"
louie@cellar.bae.bellcore.com (Paul Louie) (10/26/90)
In article <1990Oct15.030111.28548@eagle.lerc.nasa.gov> tidedu@mars.lerc.nasa.gov (William T. Dedula) writes: >Hello All; >I am currently evaluating low cost, easily implemented methods >of connecting 6 or 7 IBM PC-XT/AT's in a Local Area Network. ..stuff deleted... >I have heard that it is possible to utilize RS-232 serial ports >on each computer to implement the network. If anyone has heard >of (Or done) this, I'd be interested in knowing the BEST, and >MOST EFFICIENT way this can be done. Yes, I have tried this method once and I abandoned it. It was a good thing that my hardware supplier have a 30 days trial policy on all irons they sales. There are three major problems with this methods, performance, maintenance, and cost (eroneous assumption of saving money). 1. - Performance. All serial lan boxes, aka zero-slot lan, can only support a maximum throughput of 19,200 kps due to the limitation of the PC's serial port. Although they allow you to access files stored at another PC through a logical drive interface, the speed limitation make it impractical for you to do that. Therefore, you must store a copy of each program at each PC and file transfer the need data files before you can work. 2. - Maintenance. Due to reason stated in 1, you therefore can't have centralized control of programs and data. This eventually lead to the problem of having different version of programs and multiple version of a document. The DOCUMENT problem is a major one, since you don't have file locking no one can know if something is checked out currently. The PROGRAM problem you might be able to get away with if you work hard to keep everyone in line. 3. - Cost. Let's analyze the total cost of having a zero-slot lan vs. installing, let's say, Netware ELS II using thin-coax. We can disregard wiring cost, since this kind of installation is done by yourself and the material cost between thin-coax and phone wire are neglegible. A PLUS - if you buy Antheme's NE-1000 you get 20' of coax and a T-connector with each board. Zero-Slot: Box+Software $1000 40mb HD ($350x7) $2450 ----- 3450 ELS II: Netware $1200 NE1000 ($145x7) $1015 150mb HD w/ ESDI controller $1200 Ethernet Terminator $ 20 ----- $3435 As you can see for the same cost you'll have a system that's high performance and easy to manage. That's why zero-slot lan has never been that popular. Paul