[spork]

Greetings mac masters,
I would like to open up a can of worms and hopefully get the skinny on a possible upgrade for my g4 dual 533 digital audio PM.

I have been researching here and there about the common upgrades (OWC, Sonnet, Gigadesigns) and if I understand correctly, there are dual CPU upgrades which only change the chips and there is also a different upgrade which transforms my originally dual CPU into one chip running something faster than my original combined speed of a little over 1ghz?

Okay, is one purely better? Does one have a better price/cost benefit? I have price restrictions meaning up to perhaps $400, but that stretches my budget a bit anyway.

That part aside, what about cache, L2 and L3? What are the cache differences, how much do they matter and should I care. Photoshop CS, FCHD and DVDSP would be the most intensive programs I use, no hard core games.

thanks in advance for any and all help

[MORT A POTTY]

cache definitely matters. the 7455 based upgrades have 256K of L2 cache, the 7447A based upgrades have 512KB of L2 cache and no L3 Cache, and the 7457 based upgrades have 512K of L2 cache and 2MB of L3 cache

*these cache numbers are all "Per Processor"

the fastest upgrade will be either the 1.8Ghz 7447A based upgrade from Giga Designs, and the next fastest (very close) will be the dual 1.42Ghz 7455 based upgrade from Giga Designs. if they made a dual 1.5Ghz upgrade based on the 7457, I'd definitely say get that.

since you already have a dual system, don't go down to a single processor system...

[Amacapart]

Originally posted by spork:
my original combined speed of a little over 1ghz?

Doesn't work that way, really. If it did, the best G5 would be a 5Ghz, WOW !!!

Sadly, very few apps get much use from 2nd CPU since they have to be written to take advantage of it.

Also, the loss of L3 cache on 7447 is CRIPPLING. Don't be fooled by higher initial number frequently a lower spec 7457 with L3 will be faster than a 7447.

But don't take my word for it. A great comparison of newer upgrades can be found here:

http://www.barefeats.com/cubeup.html

In trying to get a proper "debut" for G4 X800 we contacted Gigadesigns about what fastest G4 proc was to "stretch legs" of X800 XT.

From Owen Smith there:

"Your tests might actually run faster in QS._ I have a dual 1.8GHz processor upgrade for this machine based on the 7447A (no L3 Cache)._ The fastest upgrade I have for the MDD is a dual 1.4/1.42GHz 7455 card._ This card has 2Mb of L3 cache per processor."

This echos what Mort said, Dual 1.8 7447 is just slightly faster than a dual 1.42 7457 with the cache.

Good luck, please let everyone know what happens.

[MORT A POTTY]

actually, it doesn't matter that few apps take advantage of a 2nd CPU, if you run more than one app at a time (and seriously, who doesn't?) then you will reap the benefits of it because it will balance the processes between both CPUs.

[thereubster]

Originally posted by MORT A POTTY:
actually, it doesn't matter that few apps take advantage of a 2nd CPU, if you run more than one app at a time (and seriously, who doesn't?) then you will reap the benefits of it because it will balance the processes between both CPUs.

But only if they are multi-threaded... Which may good mac apps now are, but some notable ones (Office) are not. Having said that I agree definitely go for the dual processor upgrade if you use FCP or photoshop.
Might want to wait for the new Dual 1.5Ghz 7457 card from Powerlogix.... I'm going to wait for a Dual-core upgrade card or at least a dual 7448 upgrade card

[rogerkylin]

Originally posted by thereubster:
But only if they are multi-threaded... Which may good mac apps now are, but some notable ones (Office) are not. Having said that I agree definitely go for the dual processor upgrade if you use FCP or photoshop.
Might want to wait for the new Dual 1.5Ghz 7457 card from Powerlogix.... I'm going to wait for a Dual-core upgrade card or at least a dual 7448 upgrade card

No. The OS will distrubute the workload between however many processors are available. The apps don't need to be multi-processor aware, multi threaded or anything... because the OS is multi-processor aware.

[sideus]

If the app is not coded for multi-processor, then OS X handles the multitasking job for the app, is the way I understand it.

[Abit667]

Originally posted by sideus:
If the app is not coded for multi-processor, then OS X handles the multitasking job for the app, is the way I understand it.

Sort. An application being multithreaded just means that the application its self is capable of creating multiple "threads" or tasks. Like when you look in top or the performance monitor thing each one of the things running can be a thread or a task. Some applications are written so that certain parts of them will run as seperate threads which can then be distributed to another CPU.

So here are two situations. Say there is an application that does some kind of processing on photos or something and it takes a bit of time for each one to complete. If the application were written so that each one it's doing is running in a seperate thread the os can move these threads across both cpus, allowing the job to complete is about half the time it it only had one cpu available to it.

Another is if applications are not multithreaded and written with dual cpus in mind, which most arn't. The benefits of having a dual system are still strong here. The OS will manage the load across both cpus, trying to make sure that system tasks and other applications are always able to run on a cpu that isn't loaded down. So if you were to be running an application that was doing something that required the use of the entire cpu, the os will still move things around so that anything else you're doing is going to be getting done on the next processor, meaning your computer still feels like it is running fine, when on a single system things start lagging and slow doing.