Newsgroups: comp.windows.x
Path: senator-bedfellow.mit.edu!bloom-beacon.mit.edu!news.starnet.net!wupost!howland.reston.ans.net!news.sprintlink.net!news.infi.net!taylor.infi.net!mark
From: mark@taylor.infi.net (Mark Davis)
Subject: Xterminal FAQ/Guide Ver 1.3
Organization: Lake Taylor Hospital Information Systems
Date: Wed, 05 Jul 1995 20:20:12 GMT
Message-ID: <1995Jul05.202012.21163@taylor.infi.net>
Lines: 853


             Xterminal FAQ (Frequently Asked Questions) and Guide
                            USENET- comp.windows.x
                                 Version 1.3


TABLE OF CONTENTS

0.0  Introduction

1.1  What is an Xterminal?
1.2  What is NOT an Xterminal?
1.3  Where did Xterminals come from?
1.4  How does an Xterminal work?
     What is a "host"?

2.1  How are Xterminals connected?
2.2  What are other Xterminal connection options?
     How are Xterminals connected using serial lines?
2.3  What is the minimum required serial speed?
     Can I realistically run X over a modem?

3.1  How are Xterminals installed?
     How do Xterminals boot?
3.2  How are Xterminals administrated?
3.3  What is XDM/XDMCP?
     How can I set up X to allow logins for Xterminals?
     How can I support multiple hosts for Xterminals?
3.4  What's the deal with fonts?

4.1  How are Xterminals upgraded?
     Can RAM be expanded?
4.2  What about RAM?
4.3  What about color?
4.4  What about animation?
4.5  What about sound?
4.6  What about Postscript?
4.7  What about keyboards?
4.8  What about pointing devices?

5.1  How can I increase performance?

6.1  What are advantages of using Xterminals over workstations/ distributed
     systems?
6.2  What are disadvantages of using Xterminals compared to "workstations"?
6.3  What are advantages of using Xterminals over "clones" running
     commercial Xservers?
6.4  What are disadvantages of using Xterminals compared to clones and
     commercial Xservers?
6.5  What are advantages of using Xterminals over ASCII terminals?
6.6  What are disadvantages of using Xterminals over ASCII terminals?
6.7  What are other options?
6.8  Who should use which type of equipment????

7.1  How much do Xterminals cost?


0.0  Introduction

The purpose of this FAQ/guide is to help answer some of the many typical
questions posted to comp.windows.x about various aspects of Xterminals. 
Please consult the regular comp.windows.x monthly FAQ's for information
regarding normal X concepts and terms.  I have done the best job I can to
keep the information in this document accurate and useful.  I do NOT claim
that there are no mistakes or inaccuracies in this document!  Your comments
are both welcome and appreciated   If you need to contact me:

name:          Mark A. Davis
email:         mark@taylor.infi.net
voice:         (804)-461-5001 x 431 (work)
snail mail:    Lake Taylor Hospital
               1309 Kempsville Road
               Norfolk, VA 23502    USA
               ATTN: Mark A. Davis, Director of Information Systems

I am not affiliated with any organization who produces computer equipment
or software.  This document is being maintained in my ever-so-scarce "spare
time".  If you wish, copies of this document are available in Unix
WordPerfect format, ASCII format, or PostScript format (contact me).  You
may freely distribute this document in any form, as long as you properly
cite the author :)

Another source of Xterminal information is the Xterminal listing produced
by jim@applix.com.  It is posted quarterly to comp.windows.x and contains a
very large number of terminal models, base features and manufacturer's
suggested retail prices (note that street prices are often much lower).


1.1  What is an Xterminal?

An X display terminal, or "Xterminal" as it shall be called from now on, is
a graphics display terminal capable of running the X server code,
connecting to one or more hosts, and running without the need of local
media (IE: hard drives, floppies, etc).  All Xterminals will have a some
things in common:

1)   A display of some sort (VDT, tube, LCD, etc).  They can be monochrome,
     greyscale or color.  Sizes vary from under 9" to over 19".
2)   A central processing unit (CPU) of some sort.  Many Xterminals now use
     RISC chips or specially designed CPU's.
3)   A graphics chip or processor of some sort (almost always).
4)   Local RAM.  Typically 4 MB of RAM are standard issue, with most units
     being very expandable.
5)   A keyboard device.  Many Xterminals use standard "clone" type, "101"
     keyboards.
6)   A mouse or other pointing device.
7)   A case & power supply.
8)   Server/boot software on ROM, EEPROM, etc... residing on the host or
     the Xterminal.
9)   One or more host computers of some type, which provides the platform
     on which clients are run.


1.2  What is NOT an Xterminal?

Anything which runs, in whole or in part, any of the Xserver on the host
(or not locally, from the desktop perspective).  Anything which REQUIRES
local writable media (such as hard drives and floppy drives; although, they
might be offered as an option).  Although not Xterminals, "workstations" or
IBM PC clones running Xservers can be used as Xterminals, but will be
different in certain ways and lose many of the advantages which Xterminals
have in many environments.  To make our lives less confusing and to stick
to accepted terminology, we shall call non-Xterminals used in an Xterminal
role an "Xdisplay".

Some alternative views of Xterminals allow for local writable media, as
long as the majority of the clients are running on a remote host.  But,
most of these situations involve clones and workstations being used in an
Xterminal role and were not designed AS Xterminals.  You may have to decide
for yourself!  Local media is sometimes offered as an option on Xterminals
for storing fonts, server code, etc.

Note the common mistake of confusing the terms "Xterminal" and "xterm".  An
Xterminal is a piece of hardware, while an xterm is a piece of software
running under X to allow the running of text based applications.

Another common mistake is the phrase "I want Xterminal software" or "I am
looking to emulate an Xterminal".  Both stem from confusing Xserver
software with Xterminal hardware (or hardware/software combination).

Using Xserver software, most any computer can be turned into a device which
performs many of the same functions as an Xterminal.  There are pros and
cons to this approach, which will be discussed later.


1.3  Where did Xterminals come from?

Actually, the concept of an "X Terminal" was a concept founded in X itself. 
One of the motivations for developing X was to allow graphical applications
on powerful computers to be displayed on other brands of computers or some
type of industry standard graphics terminal.... dubbed an "X" terminal.  Up
to that point, graphics terminals were not uncommon, but each had it's own
protocol for relaying and controlling graphical information.  If one had an
Xterminal, then he would be able to use any X-based software running on any
X host on any OS supporting X running over various networks.  It was a
radical concept which has blossomed into more than the designers of X (MIT)
had probably expected!  

Xterminals have been around for years, possibly 7.  They were overshadowed
by  "workstations" for some time, and have now come back into the light
again with advances in technology, the need for regaining control of
distributed systems, and/or to reduce extremely high administration costs. 

Scores of companies make Xterminals now.  They come with all kinds of
standard and optional features.  Consult the quarterly comp.windows.x
Xterminal list/posting for an idea of what is available.


1.4  How does an Xterminal work?
     What is a "host"?

Xterminals must be connected to a "host" computer to do useful work.  The
"host" is the system on which the applications programs are run.  The
graphics information, in the form of the X protocol, is sent from the
application (or client) to the Xterminal.  The software running on the
Xterminal, called the server, or Xserver, receives the drawing and
windowing commands and displays the information on the screen.  The Xserver
also gets keyboard information and mouse events and sends them to the
client running on the host.

In this manner, Xterminals truly use a "client-server" type architecture. 
Applications are CLIENTS, the Xterminal is the SERVER; the clients normally
run on a HOST.


2.1  How are Xterminals connected?

By far, the most popular method to connect Xterminals to the host is with
Ethernet.  Ethernet is a network specification which provides three methods
for connection: thinnet (which is thin coax cable with BNC connectors), AUI
(which is a DA-15 connector), or 10-base-T (which uses an RJ-45 connector). 
All these connections have similar features as far as speed and general
function.

10-base-T is quickly becoming the most popular option, because the wiring
uses standard phone type cable (twisted pair) and is easy to disconnect
from the Xterminal without bringing the net down.  Thinnet is even easier
to run cable and install connectors, but requires coaxial cable and will
[typically] cause problems on the net when disconnected from its device. 
However, thinnet is less usually less expensive in smaller installations
because no 10-base-T hubs are required.  AUI is often available to connect
to a "transceiver" for "thicknet" use.  

Many Xterminals come with all three of these connectors standard.  With
others, you must choose which of the connectors you require.  TCP/ip is the
most common lower transport protocol used on Ethernet for Xterminals.


2.2  What are other Xterminal connection options?
     How are Xterminals connected using serial lines?

Although Ethernet is the most popular method of connecting Xterminals, it
is not always appropriate.  When remote use is needed, serial
communications are required.  Most Xterminals will have either ethernet OR
serial connection methods but not both (however, more models are becoming
available with BOTH standard).  Serial Xterminals usually allow connection
using SLIP (serial line internet protocol), CSLIP, PPP, or some proprietary
protocol.  Using these methods, Xterminals can be used with direct serial
cabling or over standard modems.

"Low Bandwidth X" (LBX) is now available in R6 as a standard for
compressing serial data streams for X.  It is still in testing, and
probably not stable yet.  Although LBX might not be terribly useful over
V.32bis (LAPM) compressing modems, it should be very useful when connecting
serial Xterminals locally.

Other Xterminals offer token ring network connections as optional
equipment.  Certainly, when higher bandwidth networking standards are set,
Xterminals will probably offer those options also.


2.3  What is the minimum required serial speed?
     Can I realistically run X over a modem?

There is no minimum speed at which you can run an Xterminal, but graphics
require a lot of data transmission compared to ASCII data.  If you find a
2400 baud modem slow with text terminals, then it is absolutely futile for
X.  Some people can tolerate 9600 baud, but the key is to run it as fast as
possible for the best performance.  With remote connections, one should
consider V.32bis modems (14,400 baud/ compression), the prices have dropped
considerably.  Even so, things will not feel as zippy as ethernet :)


3.1  How are Xterminals installed?
     How do Xterminals boot?

The typical installation process of Xterminals is usually very simple. 
Most of the work is done when installing your first Xterminal.  This is a
typical sample for an ethernet Xterminal with remote boot for Unix: You
must unpack and setup your terminal first.  Next, you must turn it on and
enter an IP address (and optional name) for the terminal, the host, and the
font server.  You must specify the boot method and directories and connect
the terminal to the ethernet.  Next you must load the Xserver/boot software
onto the host (if it has not been done) with the fonts (if necessary).  You
must enter the Xterminal's IP address (and name) in /etc/hosts and make
sure you are running XDM/XDMCP.  Boot the xterminal and start working!  I
have seen typical first installs AND configurations in under an hour. 
Subsequent Xterminals can go from the box to a login prompt (ready to use)
in under 5 minutes.

Another, even more fascinating way to boot Xterminals (especially when
there are many hosts), is "bootp" (also dhcp).  Bootp stands for "BOOTstrap
Protocol", which is a method for the Xterminal to broadcast a request for
booting and the first host to respond supplies the network addresses, the
server file to download, and other relevant information.  This is similar
to the way XDMCP works for automagical display management (see that section
below).


3.2  How are Xterminals administrated?

There is very little administration with Xterminals.  After initial setup,
all Xterminal features can be controlled remotely on the host or locally in
the Xterminal's setup screen.  There are no files on the Xterminal to
secure, backup, or worry about.  Once you have any X software working on
the host with fonts configured properly, it will (magically) work on all
the attached Xterminals.  XDM takes care of logins and sessions.

Centrally located setup files are usually available so that all the
features of Xterminals can be controlled easily.  Normally, one can
configure defaults for all Xterminals, groups of Xterminals, or even
individual Xterminals.  Many Xterminals will also respond to SNMP (Simple
Network Management Protocol) commands.  This is another convenient way for
administration to remotely change configurations or even reboot/restart
devices.


3.3  What is XDM/XDMCP?
     How can I set up X to allow logins for Xterminals?
     How can I support multiple hosts for Xterminals?

XDM is the X Display Manager.  It is a utility which performs the functions
of "getty" (for character terminals) on the host to the Xterminals.  It
provides a nice login screen for users and then runs an Xsession, similar
to a .profile.  XDM is not necessary to use an Xterminal, but it would be a
strange experience without it.  One would have to, perhaps, telnet from the
Xterminal to a host, login in, set the $DISPLAY manually, and deal with
various other annoyances.

When an X session ends or terminates, XDM then calls up another login
screen.  A session is from the time a user logs in (through XDM) to the
time the user logs off.  XDM resides in /usr/lib/X11/xdm on many Unix
systems; this is where the configuration files are found.  Older Xterminals
require their $DISPLAY name to be included in a file called
/usr/lib/X11/xdm/Xservers.  XDM would read this file on boot (of the host)
to determine which ethernet devices to run XDM services for.  XDMCP is an
enhanced version of/ protocol for XDM which provides automatic services to
the Xterminals without the need for /usr/lib/X11/xdm/Xservers.  Instead,
the Xterminal and host talk to each other, enabling constant login
services.

You should always use XDMCP if your Xterminal supports it (all modern
Xterminals will).  XDMCP can also allow a list of all possible supporting
hosts to appear on your Xterminal to which you can "connect" (if this
feature is enabled and supported on your Xterminal).  This feature is
normally called a "chooser", and can be a very good way to offer login
services from more than one host.  The user can quickly choose, from a nice
menu, which host he/she wants to log into.  Note that the chooser should
not be used or enabled if there is only one host, as it will be redundant
and waste some resources.


3.4  What's the deal with fonts? 

Most Xterminals will have a few VERY basic fonts stored locally, in ROM. 
The main body of fonts, however, are usually stored on a single host.  But
this is NOT absolute!  Some Xterminals (if not most) allow you to have
fonts located on more than one host.  And if you are running X11R5 or
above, this includes the "font sever" which is a host designated to provide
font services to your Xterminal (such as supplying fonts or being able to
remotely scale fonts for you).  In any case, the font server can be a
different machine than the XDM/XDMCP host which can also be a different
machine than the Xterminal's boot host!!  Fonts can also be located on
local flash ROM inside the terminal itself, if the terminal is so equipped.

Xterminals must load fonts into their server before they can use them. 
Once fonts have been loaded into the Xterminal's Xserver, they can be used
for the entire Xsession.  Xterminals read in a table of font names (which
they can later use) into their Xserver at boot time from their font host
(this does NOT mean it reads in the fonts themselves, just the location and
name of the fonts).  During an Xsession, if you want to add more fonts into
the local Xserver, you can use the "xset +fp" command.  Note, however, that
those fonts will "disappear" from the server at the end of the session or
when the Xserver is reset.  To add them permanently, you will need to
change the Xterminal's configuration file and/or the appropriate fonts.dir
entries.  Most Xterminals will require that you hard reset the Xterminal
(or boot) so the Xserver will read in those changes.

Fonts are stored and treated in a standard way, you can consult the other X
FAQ's for more information.  Remember, however, that if you are using a
clone as a host (such as SCO, Unixware, or Interactive), the bit order of
the native fonts on those machines will likely not match the Xterminal and
cannot be used!!!  (Note: the bit order for your X86 Unix bdftosnf and such
might also be backwards by default, check the man pages).  You will either
have to obtain the correct bit ordered fonts (like from the MIT
distribution) or make 'em yourself.  BTW: many Xterminals come with certain
font converting software.  Others can read various font formats AS native,
such as certain brands of SNF, BDF, PCF, etc.  But everything is much
better if the .bdf fonts are supplied with your software applications :)


4.1  How are Xterminals upgraded?
     Can RAM be expanded?

There is usually little in an Xterminal which would need "upgrading".  One
can usually add more RAM (usually in standard 32/36 bit SIMM format),
additional pointing devices (such as digitizing tablets, light pens, track-
balls, etc), or local client ROM's with little difficulty (such as a window
manager, server code, or clients).  Xserver/boot upgrades to come up
occasionally- if you use the host to store the Xserver for the terminals,
you just load the few files on the host and all the Xterminals are
upgraded.  Some Xterminals come with "flash RAM" (or "flash ROM") which
enables one to store the server, fonts, and other code on the terminal, but
can still be easily upgraded centrally.  As for software applications- this
is host dependant.  Any upgrades done on the host are always ready for the
Xterminals.


4.2  What about RAM?

Local Xterminal RAM is necessary to run the Xserver code in the terminal,
to store server extensions, to allocate pixmaps, to store fonts, to provide
backing store, and for many other purposes.  Most entry level Xterminals
will come with 4MB of RAM.  If you don't plan on adding tons of bells and
whistles, this amount of RAM is usually plenty for Mono Xterminals.  It is
somewhat tighter for 256 color Xterminals.  As an example, just one full
screen of data on a 1024x768 screen will take about 96K for monochrome. 
For 256 color, that jumps to 768K!!  This will effect memory resources. 
There are many other factors which will determine how much RAM you will
need- such as number of applications run, type of applications, backing
store needs, number of fonts required, local clients running, etc.

Many Xterminals have an option in their setup menus which will display
information about memory usage.  You can use this to start your
investigation.  Try changing options and watch their effect on RAM.  Some
Xterminals also have clients which can warn of low memory situations. 
Others can "steal" memory from one resource to supply to another more
important one (when necessary).  My suggestion is to start with a base
amount of RAM, then read your documentation and understand how memory is
allocated and used.  Use the terminal under normal and extreme software
loads and see what happens.  If you need to add more RAM, it should be as
easy as popping in a SIMM.

Note that the more recent RISC processor based Xterminals require more RAM
than non-RISC terminals (this is only an issue for the Xserver code and
local clients).  You might want to ask your vendor exactly how much RAM
their Xserver consumes; this way you can compute how much RAM is left over. 
About 1 MB of left over RAM (after loading the Xserver, font tables, and
any local clients) seems to be the minimum you will want for monochrome
Xterminals; and 2 MB of left over RAM for color Xterminals.

Some programs make extensive use of PIXMAPS, which are regions of memory on
the Xterminal which are used to store graphics data.  This will increase
the demand for RAM on the Xterminal.  Well written X programs should switch
to host RAM if the Xterminal does not have enough RAM for additionally
requested PIXMAPS.  However, I have seen X programs which will crash if the
Xterminal says "sorry, I have no more RAM to give you".  One example is
WordPerfect for X.  In those cases, you should make sure you have enough
local RAM to run the programs you need to run.  Obtaining a loaner
Xterminal from your vendor and putting it through the works should answer
these questions.


4.3  What about color?

What about it :)  Actually, this is a good question, it covers a lot of
ground.  Xterminals are available in three basic configurations 1)
Monochrome, 2) Grey Scale, and 3) Color.  Monochrome means "one color".  In
reality it means black and white only (1 bit).  Most X software will run
fine in Monochrome.  Even Motif uses dithering to give texture and scale to
the screen.  The lowest priced terminals will usually be monochrome.  Some
people actually prefer monochrome, not only because of the price, but the
sharpness of the screen (which is usually better than color).  Monochrome
Xterminals will also be faster and use much less Xterminal memory.  This
"side-effect" further reduces the costs per seat.  

Grey Scale is both like color and like monochrome.  Like monochrome, it can
display only one "color", but like color, it can display many shades
simultaneously.  These terminals retain the sharpness of mono, and most of
the definition of color.  They are typically more expensive than mono, and
less expensive than color.  Number of "bits" of grey vary.  For instance, a
4 bit grey scale can display 16 distinct and separate shades of grey; while
8 bit can display 256 shades.  Any software should run fine in greyscale. 

Color displays obviously have the advantage of color!!!  What they give up
in price and sharpness, they gain (big time) in definition.  The
explanation of number of colors is similar to number of grey shades, above. 
All X software will run on color Xterminals.  Some Xterminals offer
"TrueColor" (millions of colors) and others over 256 colors at a time
options.

You might want to avoid 4 bit color Xterminals (16 colors).  They are rare
nowadays, but there are many X applications which simply do not run
correctly or act strange with 4 bit color displays.

The market seems to be polarizing- not only have 4 bit color Xterminals
disappeared, but it would appear that the same is happening to grey scale. 
Most companies now only offer color or monochrome terminals.  Screen sizes
vary, but 15" is fast becoming the smallest standard size (up from 14"),
with 17" and 19" sizes as options.  Of course, many companies sell larger
or smaller screens (9" - 27") as options or "specialty" Xterminals....
expect the prices to be higher, however.


4.4  What about animation?

Indeed, animation is possible on Xterminals.  However, if you plan to do
this a lot then you will need 1) more network bandwidth than typical and 2)
more hosts than typical.  You might also consider workstations as a better
alternative.  Many manufacturers are releasing so-called "Multimedia"
Xterminals which will support the viewing of MPEG video clips directly from
the host.  Typically, the MPEG (or similar) clips are displayed in a small
window (perhaps 2" x 1.5" to twice that size).  Network latency can cause
flow breakup.


4.5  What about sound?

All Xterminals I know of support at least BELL through xterm-like clients,
which is a beep mapped to ASCII code 7.  All Xterminals should also be able
to produce a beep through the X "Beep" function.  Key-click sounds are
usually available, although you might have to use "xset c" to turn it on.  

Newer Xterminals support various tones and multi-voice and even multi-
channel sound.  Some models even support playing back of digitized sound
and recording it too.  "NetAudio" (or NAS, Network Audio System) seems to
be the current direction in sound capabilities for the moment; although
there are other forms too.  It seems the "standards" have not really been
set by the market quite yet.  Some Xserver software already supports direct
playing of .au .voc .wav .snd and many other sound file formats.  Another
option you might want to look for is AID support (Audio Intercept
Driver/Server) which allows emulation of Sun's /dev/audio and related
devices.

Often, the audio functions are set up in "client-server" style, in the true
spirit of X.  The audio functions are intercepted and processed by a
seperate process (server) running on the Xterminal (with the Xserver).  Any
client could connect and use the server for playing or recording of audio. 
I have used multimedia Xterminals with sound and it is quite impressive
(although often hard to figure out what to do with those features besides
Xmosaic :)  ).


4.6  What about Postscript?

Postscript is a [mostly] vectored way of sending graphics data and scalable
text.  "Display Postscript" is gaining popularity from the market as a way
to send graphic and text information.  If you have need for Display
Postscript under X on your Xterminal, then make sure your vendor has either
local DPS support (preferred) or host based support.  Note that local DPS
will increase your need for local Xterminal RAM.  You will probably find
that you don't need DPS, since few programs require it.  The most notible
exception is Sun's AnswerBook, which requires DPS for viewing the manual
pages (even though the rest of the program is standard X).  This, IMHO, is
not a good move on Sun's part.


4.7  What about keyboards?

Most Xterminal models offer a variety of keyboard choices.  Not
surprisingly, the most popular is the IBM clone or "101" keyboard type. 
But you can also get DEC, SUN, and other "style" keyboards.  In fact, most
Xterminals use standard PS/2 type connections now, allowing you to connect
any type of "standard" keyboard you want.  But, if you connect a different
keyboard than one offered by the manufacturer, check to make sure it will
work properly!

If you have need to use a barcode reader on the terminal, you can probably
use the "wedge" type, which goes between the terminal and keyboard.


4.8  What about pointing devices?

Most Xterminal models come standard with a motion/digital-counter type
mouse.  Some offer optical sensor (IE- special pad type mouse) or other
types of mice.  Many models support standard PS/2 type connections,
allowing the connection of many types of pointing devices through the mouse
port, like trackballs and pointer sticks.  Many models also support the
connection of touch-screens, digitizer pads, and light pens.  Some non-
mouse and trackball pointing devices will require special drivers or
extensions.... always check with the manufacturer for information about
compatibility.

Touch screen Xterminals are becoming very popular for use in information
"kosiks".  This is when a terminal is made available to the public which
can be used to obtain on-line information.  You may have seen such an
arrangement in a business lobby.  Supposedly, a restricted version of
Mosaic will be available for such uses soon.


5.1 How can I increase performance?

Start with an Xterminal will good raw X performance.  Remember that mono
Xterminals will always have significantly more performance than their color
counterparts.

Adding memory is always a good move.  The reason for this is that you can
enable more performance oriented options in your Xserver.  For example,
turning on local backing store to "ON" or "ALWAYS" can really make a visual
difference in performance.  The reason is that the clients will not have to
update their windows when an expose event is caused.  Instead, the Xserver
simply uses local RAM to store the contents and zaps the information back
on the screen.  The not only looks faster, but also uses less net traffic,
and less host/client time.

Font caching is another good move.  Many Xterminals can cache all the fonts
which have been loaded already for a client.  When the client is closed,
the fonts sick around in RAM, ready for use again when needed.

Some people think local clients are the answer to increasing performance. 
Actually, this is not usually the case.  They do increase performance some,
and reduce net traffic a little, but are often not worth the cost (they
often have to be purchased as options) or RAM, since they will eat up local
Xterminal RAM.  The most accepted local clients at this time are window
managers, various xlocks, setup programs (usually necessary), display
postscript, and telnet.

Perhaps the single most important way to keep performance high is to not
overload the host or net with useless crapola.  An example is a simple
screen-saver with the famous "QIX" pattern.  Just a few users running this
client can slow down a network segment with useless data.  Avoid constant
and unnecessary animation; examples are: xeyes, xclock with sweep hand,
dclock with seconds, xlock with animation, xlife, xmaze, ico, etc, etc,
etc.  If you must run intense animation or constantly moving/updating
clients, you might consider adding more hosts and more network segments to
distribute the loads.  Use common sense when configuring the hosts; also
consult standard X documentation and other FAQ's for information about
increasing X and host performance.


6.1  What are advantages of using Xterminals over workstations/ distributed
     systems?

1)   Installation time/cost-  Xterminals, unlike workstations, need only a
     few moments of configuration time.  This is not limited to
     installation, but replacements too.  When an installation is large,
     this can amount to thousands of dollars per month savings.

2)   No multiple OS's to support-  Xterminals do not have a time-demanding
     OS to maintain and support.  Instead, they share (divide) the support
     cost of a fewer number of hosts.

3)   Security- Xterminals are inherently secure.  There is no local
     information stored on a Xterminal which can be removed.  No hard drive
     to steal, no floppy to remove information or inject viruses or
     unauthorized programs/data.  Physical security is almost a non-issue
     when set up appropriately.

4)   Initial Hardware Cost-  Xterminals cost much less than workstations. 
     However, one must not forget that the host or hosts which support them
     also bolster some of the overall cost.  But, most systems have such
     larger hosts anyway.  Using Xterminals can maximize your existing
     investment.  Otherwise, prices are still typically lower for, say 10
     Xterminals and a suitable host compared to 10 typical workstations. 
     Even in a mostly distributed system, one can still add Xterminals here
     and there to maximize hardware and support investment when needed.

5)   Upgrading-  Xterminals require little upgrading.  They have been
     referred to as a "desktop commodity display", meaning the support
     staff can focus on the much fewer number of hosts.  When upgrades are
     necessary, Xterminals involve much less work and time.  When equipment
     finally becomes totally obsolete, replacement costs are still much
     less.  This normally means a longer equipment "lifetime".

6)   Application Maintenance-  Instead of upgrading lots of copies of
     applications maintained on scores of separate machines, this can be
     done for fewer host machines.  Since X is a standard protocol,
     compatibility of the desk units is rarely a problem.  X applications
     can normally run on the host can displayed to any number or type of
     Xterminals.

7)   Media-  There is no mechanical media in an Xterminal to fail or
     backup/restore.

8)   Misc- Xterminals use less electricity, produce less heat, make less
     noise, and take up less desk space.


6.2  What are disadvantages of using Xterminals compared to "workstations"?

1)   Layout-  What is an advantage to one person is a disadvantage to
     another!  Xterminals do not [normally] allow for much local processing
     of information.  This can hurt if you need LOTS of graphics processing
     over a large number of people.

2)   Dependency-  Xterminals ARE dependant on the host(s) for
     functionality.  Although the disadvantage of dependency can be greatly
     minimized through the use of multiple hosts or better maintained hosts
     (compared to lesser maintained workstations), the dependency is still
     there.

3)   Upgradability-  Although most people buy Xterminals as commodity
     display devices, they are still less upgradable than workstations. 
     Sound could be a good example.  (Some new Xterminals are, however,
     much more upgradable than previous models).

4)   Overload- With Xterminals, more attention has to be paid to
     appropriate loading and sharing of common resources.  Peak load times
     can also be a problem if CPU reserves or multiple hosts are not
     available.


6.3  What are advantages of using Xterminals over clones running commercial
     Xservers?

1)   Installation time/cost-  Xterminals, unlike clones, need only a few
     moments of configuration time.  When an installation is large, this
     can amount to thousands of dollars per month savings.  Xterminals are
     usually almost ready to use- straight from the box.

2)   No multiple OS's to support-  Xterminals do not have a time-demanding
     OS to maintain and support like most clone/Xservers still have (this
     is especially true for those based on MS-"Windows").

3)   Compatibility-  Xterminals come as a complete, integrated unit.  No
     time has to be devoted to investigating appropriate hardware and
     software combinations and interaction problems.  With clones, every
     component becomes a potential problem.

4)   Warranty/Support-  Xterminals come as a complete, integrated unit.  A
     complete warranty covers the entire unit.  Support is often direct,
     and without multiple vendors pointing fingers at each other.

5)   Security- There is no potential for local information being stored on
     a Xterminal which can be removed or lost.  No hard drive to steal, no
     floppy to remove information or inject viruses or unauthorized
     programs/data.  Physical security is almost a non-issue for Xterminals
     when set up appropriately.  If necessary in your environment: it is
     difficult to prevent non-approved/illegal/inappropriate applications
     from being run on clones, regardless of their configuration.

6)   Initial Hardware Cost-  Xterminals often cost less (sometimes much
     less) than comparable clones/Xserver combinations.  If you have to
     research and/or assemble those clones and suitable software, don't
     forget to add those costs on top of the hardware!

7)   Upgrading-  Xterminals are often easier to upgrade through centralized
     storing of Xservers or through flash-RAM.  Plus, upgrades are
     typically related to a single host purchase.

8)   Media-  There is no mechanical media in an Xterminal to fail or
     backup/restore.

9)   Misc- Xterminals use less electricity, produce less heat, make less
     noise, and take up less desk space.


6.4  What are disadvantages of using Xterminals compared to clones and
     commercial Xservers?

1)   Layout-  What is an advantage to one person is a disadvantage to
     another!  Xterminals do not [normally] allow for much local processing
     of information.  This includes local running of MS programs.  If this
     is a large part of your orientation, then Xterminals will certainly
     not work as well (although WABI might fix this aspect, at least).

2)   Upgradability-  Although most people buy Xterminals as commodity
     display devices, they are still less upgradable than clones.  (Some
     new Xterminals are, however, much more upgradable than previous
     models).

3)   Reusability-  Xterminals cannot make use of most existing clone
     equipment.  [It was pointed out to me, however, that many Xterminals
     CAN reuse clone-type monitors, keyboards, mice.]  Nor can they be used
     for any other purpose besides running remote X applications (even if
     some of those applications are WABI/Merge type).

4)   Performance-  This is a touchy issue.  I can safely make the following
     comment: "At the current point in time, the AVERAGE Xterminal has a
     much higher X performance compared to the AVERAGE clone/Xserver". 
     Technology changes fast people- I can put together a clone now which
     will outperform most Xterminals (although, it will TYPICALLY cost
     more).  One thing is for sure- the low end Xterminals almost always
     beat low end clones to death on performance.


6.5  What are the advantages of running Xterminals over ASCII terminals?

1)   X- Xterminals run X and ASCII terminals do not :)

2)   Graphics- Although many ASCII terminals now support true graphics
     using bit-image or tektronix vectors, Xterminals still have a much
     more robust variety of support.  And graphics processing for
     Xterminals is local, on the terminal, not on the host.

3)   Speed- In many cases, Xterminals have faster response time.  This, of
     course, is completely tied to the environment in which they are being
     used.

4)   Connectivity- Xterminals support serial, ethernet, and token-ring. 
     Usually, ASCII terminals only support serial.


6.6  What are the disadvantages of running Xterminals over ASCII terminals?

1)   Cost-  In ALL regards, ASCII terminals are the least expensive options
     for any desktop in any situation.

2)   Support-  ASCII terminals require less support and less trouble-
     shooting.

3)   Load-  ASCII terminals are much less load on hosts than Xterminals,
     usually because of the applications being run.


6.7  What are other options?

There are other options for desktop displays which this document will not
cover, such as "multi-console" solutions, Qume "X-Displays", AlphaWindow
terminals, etc.  The reasons are varied, but include the lack of experience
by the author, and general lack of interest by most out there.  Assuming I
get new or more information and interest changes, it will be added.  I do
want to point out another solution which is interesting- using one of the
free Unixes, such as Linux or BSD/Free as Xservers for clones.  Although
most businesses will not be interested in these types of solutions, they
are notable just the same.  Such solutions are gaining popularity and
interest as the software is refined and more people install them.  This
differs from workstations primarily because of the unbundling of the OS and
other components.  Generally, if they are used in a remote-X role, you
might consider them as sections 5.3 & 5.4, above (with more emphasis on
configuration and maintenance time).  If they are used in a workstation
role, you might consider them as sections 5.1 & 5.2, above.


6.8  Who should use which type equipment?

That is impossible to answer.  There is no one type of typology which will
work everywhere, or sometimes even in one installation!  You have to decide
for yourself.  You would do a disservice to your users and your
organization if you do not consider all the viable options for display
solutions.  If I were FORCED to make a quick summary, it might turn out
like this (please note, you MUST do more research than relying on this
oversimplification of desk-top devices!):

Workstations-  A way to bring distributed and centralized processing to a
               desk top.  Typically necessary for those who need lots of
               local processing for things such as intense graphics,
               simulations, or engineering applications.  More expensive
               than most solutions, but usually most flexible too.

Xterminals-    A way to bring low cost graphics to desktops which lowering
               escalating maintenance and support costs.  Not good for
               those who need local processing, but can be used in a wide
               variety of typologies, including disparate systems and even
               within distributed networks.  A great compromise between
               workstations and regular terminals.

Clones/X-      A way to bring X graphics to those who have or need clones
               too.  Ideal for reusing existing clone equipment.  Flexible,
               but usually not as fast or elegant as workstations or
               Xterminals.  Often difficult to standardize and keep control
               over, but allows running various applications in deferring
               environments.

ASCII Terms-   The lowest cost way to bring computing power to the desktop. 
               Very effective for most business applications and those not
               requiring much graphics.  Modern ASCII terminals have more
               features than ever before, but are not suitable for local
               processing or highly flexible needs.


7.1  How much do Xterminals cost?

This is a difficult question to answer.  Many companies now make
Xterminals, and there are more new entries into the Xterminal market each
month.  There is a regular [quarterly] posting in this group
(comp.windows.x) which discusses many of the current models and prices. 
Keep in mind that list prices often vary WILDLY compared to street prices. 
And- there is no magic percent which all vendors discount for quantity or
to resellers.  Pricing of Xterminals will vary greatly depending on
features, speed, and options.

Pricing of somem Xterminal hardware is independent of the Xserver software! 
You must factor this into your overall price.  It can hurt you if you just
buy one terminal, yet become insignificant if you buy 100.  This is because
the bulk of MOST Xserver software cost is based on the number of hosts NOT
TERMINALS.  So it is often a one-time cost which can vary from $50 to $1000
(and it is sometimes free).  Be careful to research that the terminal price
includes EVERYTHING you need (like keyboard, optional local clients, Motif
runtime license fees, etc).  

Please take these *estimates* with a grain of salt:  The average entry
prices into true Xterminals is about $800 for a "medium"  (70K Xstones)
monochrome, $1100 for a "fast" (120K) monochrome, $1400 for a "medium"
(70K) color, and $1800 for a "fast" (120K) color.  (All with 14 or 15"
monitor, 4MB RAM, ethernet, KB, mouse, etc).  But some large screen, very
high performance color Xterminals can run over $3000!

-- 
  /--------------------------------------------------------------------------\
  | Mark A. Davis     | Lake Taylor Hospital | Norfolk,VA (804)-461-5001x431 |
  | Director/SysAdmin | Information Systems  |    mark@taylor.infi.net       |
  \--------------------------------------------------------------------------/


Date: 3 Feb 1998 00:36:13 GMT
From: Dan Hollis <goemon@sasami.anime.net>
Newsgroups: comp.terminals
Subject: Re: NCD 19r X terminals - What are they worth?

Erik Voldengen <bbcbike@user1.teleport.com> wrote:
: Anyone know what NCD 19r x terminals are worth?  What's a fair price
: to pay for one of these?  Thanks!

$150 tops. $200 if they include the software and manuals.

(typing this as we speak on an NCD 19r via x2x from my linux box :-)

-Dan


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