[G4] Upgrade Sawtooth to DP?

[Philip Robar]

On Mar 21, 2005, at 7:01 AM, Mel Krewall wrote:

> "Fully symmetrical" is somewhat of a misnomer. Each application must 
> be
> written to be "threaded" to take advantage of mulitprocessing.

You're confusing operating systems and applications, and multi-tasking, 
multi-processing, and multi-threading.

First of all both symmetrical and asymmetrical OSs can be multi-tasking 
in that more than one program can be alive at a time.

"Fully symmetrical" refers to the operating system's ability to take 
advantage of multiple processors, even if the applications don't. A 
symmetrical OS will actually run multiple processes at the same time 
and schedule and migrate them between processors as needed. (It's over 
simplifying things, but for the purposes of this discussion a process 
roughly equals a program.) Linux, Windows XP Pro, Sun's Solaris 2 and 
Mac OS X are symmetrical.

Mac OS Classic, Sun's Solaris 1 (a.k.a SunOS 4.x) and Windows XP Home 
(and older) are asymmetrical in that even though the OS supports 
multitasking only one program can actually run at a time - even if 
there are multiple processors available. The extra processors go 
unused, unless you run programs that are multi-threaded. Multi-threaded 
refers to an application's ability to use multiple processors - in 
effect the program is written to run multiple light weight little 
"programs".

Under Mac OS X your ability to take advantage of multiple processors is 
not an issue of old vs new hardware (assuming proper implementation of 
the hardware in both generations), but one of what programs you run and 
your work habits. Most programs are not multi-threaded, so unless you 
regularly run more than one processor intensive application at a time 
or you regularly use a multi-threaded application you would be better 
off with a single faster processor (and sufficient memory) than with 
significantly slower multiple processors.


Phil