[G4] Single or Dual??

[Mike Tweedie]

Excellent post Phil, thank you.

I do a lot if image editing, and now spend lot of time restoring vintage
photos. Next step for me is to start stitching some video together, but
nothing major.

Though I don't specifically need dual, I will be using an OS and apps that
can leverage the extra CPUIs. Just not sure it's worth the extra dough at
this point.

Thanks again.

Mike



> 
> On Dec 13, 2005, at 5:10 AM, Aaron wrote:
> 
>>> Date: Thu, 08 Dec 2005 16:48:19 -0500
>>> From: Mike Tweedie <mac at springerlabs.com>
>>> To: "A place to discuss Apple's G4 computers."
>>> <g4 at listserver.themacintoshguy.com>
>>> Subject: [G4] Single or Dual??
>>> Reply-To: "A place to discuss Apple's G4 computers."
>>> <g4 at listserver.themacintoshguy.com>
>>> 
>>> I just picked up a G4 Sawtooth 500Mhz ... it's time for a new
>>> processor.
>>> 
>>> [snip]
>>> 
>>> Single or Dual?
>>> 
>>> Looks like I can get a dual for just a bit more than a single, see
>>> here;
>>> https://eshop.macsales.com/item/PowerLogix/PF47D1200DA/
>>> 
>>> What are the groups thoughts? 1.2Ghz Dual or 1.8 Single?
>> 
>> Having observed CPU usage in my Dual 867 MDD using the CPU Monitor
>> part of Activity Monitor, I would say that, presuming you're
>> running OS X (Panther or Tiger, and probably even earlier
>> versions), you'll get close to 100% usage of the dual processors,
>> so that a 1.2 GHz Dual will be almost as fast as a 2.4 GHz single. ...
> 
> Wouldn't it be nice if it were this simple. A single processor will
> always be as fast or faster overall than multiple processors that sum
> up to the same speed because it doesn't have the overhead associated
> with distributing a task between the multiple CPUs. To take advantage
> of multiple processors an application has to be properly multi-
> threaded, and there's no guarantee that the applications that you
> care about or might care about in the future will be. Put another
> way, multi-threaded applications always run measurably, and often
> noticeably, slower on multiple processors than they do on a single
> fast-as-the-sum-of-the-multiple-processors machine.
> 
> So why would you want multiple CPUs? There are a couple of scenarios
> where multiple CPUs make sense.
> 
> The most obvious case is where the fastest CPU available isn't fast
> enough for your needs. In this case you have no choice but to figure
> out how to divide the task in question up between multiple processors.
> 
> Two, for whatever reason sequential processing of applications is
> unacceptable. For example it may be required that you get a constant
> flow of data from multiple applications and the OS's scheduler can't
> or doesn't divvy up processor time acceptably. Or it may not matter
> how fast a set of multiple applications run, but the applications are
> time sensitive enough that they need dedicated resources such that
> they are always ready to run. Multiple processors make it much more
> unlikely that any single application will take over a machine and
> make it unresponsive - particularly to interactive use.
> 
> I would always prefer to have a single processor that is twice as
> fast as 2 dual processors for a desktop machine. I rarely run more
> than one important task at a time, I want that particular task to run
> as fast as possible, and I'm willing to trust that the OS's scheduler
> will keep the machine reasonably responsive for interactive use.
> 
> Mike's case isn't as simple as the one that Aaron posited. As Aaron
> pointed out there may be significant differences between the CPUs in
> question. This makes it impossible to choose between them without
> knowing what Mike intends to do with the machine and how the
> performance of the CPUs compare. Note that some of the recent faster
> clocked G4 processors have smaller caches and different enough
> designs that they are not as fast as you might expect them to be, but
> they run cooler which may be important to some situations.
> 
> Also not that early Sawtooths are not multi-processor compatible.
> 
> 
> Phil
> --
> We cannot defend freedom abroad by deserting it at home. -- Edward R.
> Murrow
> 
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