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In article <BwrxtD.MMw@alsvid.une.edu.au> dmiller@elli.une.edu.au writes:
>What is this "X-Windows" I see referred to?  I assume it is a Windows
>version for cooperative processing?
>
>Furthermore, I have heard nothing but moans and groans about it's
>performance.  Is it any good, or too much of a resource pig?
>
>Thanks for the help.


"X-Windows" is essentially a *protocol* to allow the separation of
processing from presentation.  Both components talk to an "X" layer.
The two components can be on different machines, which may well have
completely different architectures.  Various window managers can be
built on top, to give different GUI's (Graphical User Interface's) with
distinctive look and feel.  One processing component can, at the same
time, talk with several presentation components on divers
architectures.  This is normally described in terms of clients and
servers.

The "X" system works in well with the "Open Systems" philosophy, can
makes it easier to choose the most cost effective machines for the
client and server applications in a network.  There is no longer any
need to be locked into one manufacturer, for all your "boxes" in a
network.   One common solution is to buy, one or more, very powerful
boxes to host server applications and a larger number of "X-stations"
to support users.  These "X-stations" provide very good performance
for reasonably low cost.

Performance will obviously be inferior to a well designed single host
GUI system like an Acorn Archimedes running Risc-OS, but "X-windows"
is designed to be run over a network.


Gavin
-- 
Tomorrow's Society                              | flower_g@kosmos.wcc.govt.nz
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>"X-Windows"

Or, to use its official name, "the X Window System".  One advantage of
calling it that rather than "X Windows" is that people are less likely
to mistakenly think it has anything to do with Microsoft Windows.  (Yes,
there probably exist X server packages that run under Microsoft Windows,
but there exist many that don't, and I don't know of any X client
packages that run under Microsoft windows, at least at this point.)

X clients are graphical applications, whether a word processor, or a drawing
program, or a CAD package, or....  X servers are, generally, machines with a
display and input devices such as a keyboard and mouse.  The X client
program sends requests to the X server, asking it to, for example, draw
things in a window; the X server sends back replies to those requests,
and also sends messages indicating that the user has pressed or released
a key, or has moved or pressed or released a button on the mouse.

Most general-purpose computers running X client code probably run a UNIX
variant; VMS probably comes second.  X servers can be:

	a program running on a desktop computer, as is the case with,
	for example, PC's running UNIX, or workstations;

	a program running on an "X terminal" (which the poster to whom
	I'm following up called an "X-station").

The X server can be running on the same machine as the X client software
(as is the case, for example, for the window in which I'm typing this
message), or it can be running on a different machine, with the
connection between the X server and X client being over a network.

Gavin.Flower@comp.vuw.ac.nz (Gavin Flower) writes:

>In article <BwrxtD.MMw@alsvid.une.edu.au> dmiller@elli.une.edu.au writes:
>>What is this "X-Windows" I see referred to?  I assume it is a Windows
>>version for cooperative processing?
>>
>>Furthermore, I have heard nothing but moans and groans about it's
>>performance.  Is it any good, or too much of a resource pig?
>>
>>Thanks for the help.


>Performance will obviously be inferior to a well designed single host
>GUI system like an Acorn Archimedes running Risc-OS, but "X-windows"
>is designed to be run over a network.

Gavin, 
	Although there is some truth in what you say, my experience tells me
that it ain't necessarily so.  No doubt there is overhead in formatting the
packets, sending them across the net, decoding them on the other side, etc.
However, the X-server relieves the X-client (the X-client is the program, but
in this instance I use "X-client" to mean the computer system on which the
program is running) of certain chores, such as manipulating bit maps, etc.
Thus, you have 2 processors running in parallel, more or less.  Also, the 
X-server can be implemented using a speciallized processor, such as one of the 
TI34xxx  chips, while the client is implemented using a general processor, 
such as a 68xxx, 80x86, or VAX etc.
	My experience running the X demonstration ICO on a VAXstation 3100
with VMS 5.4-3 vs. on a VXT 2000 connected to that same VAXstation is that
ICO runs faster on the VXT.  That is the extent of my testing.  You might be
right in the general case, but the answer isn't that simple.

Warmest regards


Jeff Silverman, Boeing Commercial Airplane.
silverman@ilvc.boeing.com

In article <4065@bcstec.ca.boeing.com> silverm@bcstec.ca.boeing.com (Jeff Silverman) writes:
>Gavin.Flower@comp.vuw.ac.nz (Gavin Flower) writes:
[...]
>>Performance will obviously be inferior to a well designed single host
>>GUI system like an Acorn Archimedes running Risc-OS, but "X-windows"
>>is designed to be run over a network.
>
>Gavin, 
>	Although there is some truth in what you say, my experience tells me
>that it ain't necessarily so.  No doubt there is overhead in formatting the
>packets, sending them across the net, decoding them on the other side, etc.
>However, the X-server relieves the X-client (the X-client is the program, but
>in this instance I use "X-client" to mean the computer system on which the
>program is running) of certain chores, such as manipulating bit maps, etc.
>Thus, you have 2 processors running in parallel, more or less.  Also, the 
>X-server can be implemented using a speciallized processor, such as one of the 
>TI34xxx  chips, while the client is implemented using a general processor, 
>such as a 68xxx, 80x86, or VAX etc.
>	My experience running the X demonstration ICO on a VAXstation 3100
>with VMS 5.4-3 vs. on a VXT 2000 connected to that same VAXstation is that
>ICO runs faster on the VXT.  That is the extent of my testing.  You might be
>right in the general case, but the answer isn't that simple.


Very true - the paragraph quoted from my may have seemed anti-network
and anti "X", but it wasn't meant to be.

I believe that the most cost effective way of giving a large number of
people lots of computing resources is to have a relatively small
number of high powered servers selected to be the best for the range
of software required and a larger number of workstations of various
sorts.  In this situation, it is unlikely that everybody will need a
really high end grsphics workstation, and some could probably be
serviced adequately with a character only terminal.  

There is some software that will spread the load over however many
hosts that are available.

Obviously, a single box can deliver more effective processing power,
as a percentage of what is theoretically, than a network.  However, a
network can allow the several boxes to cooperate, to deliver more
effective processing power than any single box, also this can be
tapped by anyone (who is authorised) on the network - they don't have
to be physically in front of a particular box.

How significant the performance degredation is, depends on the ratio
of the overhead involved to the gains, "obviously".

On a side note, I've been surprised at the slowness of window
refreshing on some machines with a high mips rating, compared to a
machine with a much lower one.  I could give brand names, but I'm not
trying to start a flame war.  Besides, care has to be taken to allow
for the different processing loads that the machines may have had,
that was not visible.  Though in the case I'm thinking of, this should
not have made as much diffrence.

The subject of objective benchmarking of distributed systems, has
come up, but I haven't seen much comment about it here - even about
the principles. 


Gavin
-- 
Tomorrow's Society                              | flower_g@kosmos.wcc.govt.nz
    Depends on                                   ----------------------------
Today's Children  - help us raise them properly! 
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