-- Jim Dynes <[EMAIL PROTECTED]> Lithexcel Printing Albuquerque, New Mexico
From: "Stewart, Brian C" <[EMAIL PROTECTED]> Reply-To: "G-List" <[EMAIL PROTECTED]> To: "G-List" <[EMAIL PROTECTED]> Subject: Re: which is better, dual-500mhz or 733mhz G4 Date: Thu, 30 Sep 2004 11:05:25 -0600
Please make your argument a little clearer...
> The only problem with a duel processor is that the software you use has to
be written for a dual. Otherwise you are only using one.
Mmm... Yes... A program must be written as a multi-threaded task to be able to run on both processors at the same time. Otherwise the process (task) can only run on one CPU at one time.
This is a mute point!
Most Applications run many programs or tasks at the same time. Take the
freeware apache httpd server. This is the Internet Standard for Web Servers.
It by default runs as a non-threaded task. Ok so one instance of the program
can only run on one processor... But also by default it spawns 5 or 6
instances of it self in memory up to a maximum that is configured in the
httpd.conf file. Each instance can run on a single CPU.
My Point...
Two users connect to your web server, two instances of the httpd daemon fire
up in memory. Each instance will run on a single CPU. Each user gets to take
advantage of simultaneous operation on your Dually G4.
Does it really matter that the application it self is not multi-threaded?
If you go to your shell (terminal) and run the command "ps -aux" you will
see a number of processes in a mixture of states. IDLE, SLEEP, RUN and
possible ZOMBIE. I can not say how many processes are in IDLE or SLEEP but I
can say how many processes are in RUN on a single CPU system at one time.
ONE!
Does it really matter if applications and the OS are not multi-threaded?
A modern operating system - moving away from DOS and Mac OS Classic - are multi tasking capable, Yes Mac OS Classic is a multi-tasking system but it does not have protected memory so it is sitting out on this one.
Multi-tasking capable means more then one process in can be ran at
"one-time" but the catch is. Only one thing can run at one time because you
have only one processor. pre-emptive multi tasking gives the illusion that
many things are happening at once but the CPU is giving equal time slices to
many tasks over the period of time. Sometimes when a Disk I/O is required a
task will "sleep" and give up it's turn on the CPU but when multiple tasks
are prepared to run they must all wait there turn in line for the CPU.
Two CPU's will allow you to do two things at once.
Does it really matter if applications and the OS are not multi-threaded?
A multi-threaded program is a task that can break down into smaller tasks
that can run simultaneously on multiple processors. This causes a lot of
programming overhead and is not required for most applications. Applications
that have a requirement to run on multiple processors will be
multi-threaded. Databases and Large Application services are candidates for
multi-threaded operation.
I believe some of the LINUX QUAKE-III graphics routines were written as multi-threaded tasks to take advantage of a multi-processor system.
I believe some filters in photo shop have multi-threaded extensions but I am
not 100% sure.
The exact same comparison can be made of the G3 and G4 processors. If you run an application that does not take advantage of the altivec engine then there is no point to getting a G4. The difference is, applications do not need to be written to take advantage of multiple CPUs to take advantage of multiple CPUs.
Does it really matter if applications and the OS are not multi-threaded?
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