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Dual processors


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Not that you want TOO technical and answer but... in order to take advantage of dual processors, the progam has to be written for it. That is refered to as multi-threaded. Most programs are not multi-treaded, such as word, etc... why? because you never use more then 5% of your CPU power to write in word. Photoshop is not multi-threaded either, unless it is a recent thing I'm not aware of. Rendering engine are. You need a lot of processor power to render. Rendering is one of the most intense thing a computer does. Even more then computer games. Good rendering engines are completely multi-threaded and use two processors to do everything from shadow building to rendering. For the most part, you will probably only take direct advantage of dual processors if you do a lot of rendering, and I would agree with quizzy... about 1.8 times faster, depending on what rendering engine you are using. An added bonus to a multi-proc computer is a more stable computer which is really good at multi-tasking. Unless you are rendering, you can easily do lots of things on your computer all at once. That is because your OS is multi-threaded. Keep in mind that you simply can't add a second processor to a dual processor motherboard without re-installing you operating system.

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well matt, open your task manager see what both processors are doing, and perform some have rescaling on a picture in photoshop, I mean very heavy, so make a picture 640x480x72dpi into a picture of 640x480x1200dpi and see what the 2 processors are doing. Its depends on what kind of action you are doing in photoshop, not all filters are multi-threaded...

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photoshop only uses the second cpu when calculating filters.

still, dual cpu's make a system much smoother, when you switch tasks, open windows etc. because windows is multi threaded.

3dsmax uses the second cpu for rendering (its almost double as fast)

the screen performance won't really change. a fast P4 has a much better screen performance than a dual-p3 which might be faster for rendering, even when using openGL (3d acceleration is heavily CPU dependent).

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hi matt,

 

a few tips on ps:

- set your scratch disk to another disk than your startup disk

- set memory usage to about 80-85% instead of it's standard 50%

 

you can enter the general settings by pressing ctrl+K ;)

 

rgds

 

nisus

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Remember the advantage of dual processors is not just in multithreaded applications. When running a multiprocessor OS, you can set the affinity of various applications and programs on cpu 1 or 2.

 

Example: You could be running Viz4 on CPU 1 and Photoshop on CPU 2. Thus allowing yourself to do texture work or post work in Photoshop, while Viz 4 calculates the radiosity on CPU1, basically giving you the functionality of two machines in one.

 

This is extremely useful if you only own a single system, as it allows you full usability of the computer while rendering, calculating radiosity, or doing any computationaly advanced tasks which take an extended period of time. Just set the application to realtime on CPU #2 (take it off cpu 1) then use the machine as normal. The realtime app will suck up 100% of CPU #2 while cpu#1 handles all other apps and programs.

 

Seems to make the renders take less time when you don't have to sit around waiting for it to finish :) .

 

[ August 20, 2002, 07:40 PM: Message edited by: Greg Hess ]

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Greg,

 

Question for you. Is there a benefit in doing this? I've had VIZ and MAX rendering on my dual and still been able to work without any lag. I thought that if another app opened and both were set to normal and on both CPUs that they would simply share the resources.

 

Afinity seems to be the hot topic these days and I was really curious how perfoamnce productivity is affected one way or another. I figured it was only useful for apps that didn't like to play well on 2 processors. Thanks for the insight.

 

Jeff

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Hey Jeff,

 

Affinity is useful if you want maximum play out of another app. By dividing processors you can control the allocation of resources more closely, thus preventing cpu lag from a heavily multithreaded section of a render. You'll find that though sometimes the system will be snappy while rendering or calculating radiosity...it sometimes won't when it hits a rather strenuous part of a calculation. Then even IE will take tremendous delays to open. I usually only set affinity when I don't have to have a render done for a few hours and need to finish working on another scene. (Render with one copy, open a second on the other cpu for modeling etc). Now that I have DR with Vray, I just use a whole nother system to do the rendernig.

 

Setting affinity really comes into play if you have a quad system. Because of the inefficencies of a quad box, you can actually INCREASE system performance by setting affinities. (Because of the single threaded nature of max/viz and other renderers, setting affinity and forcing two copies of max to each run on two cpu's, is quite a bit faster then having one copy run on 4).

 

So in conclusion...affinity allows you to squeeze more performance out of whatever tasks your doing. Micromanagement of the cpu's or what not.

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Hi Greg,

 

Maybe those are real stupid questions, but I'll shoot it anyway:

 

- in your opinion: what is best?

1) set max on 1 cpu / another app on the other cpu

OR

2) set max on both cpu's with affinity low / other app on both cpu's too but affinity normal

- why?

 

tnx

 

nisus

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- in your opinion: what is best?

 

A max only machine, preferably a dual processor one, with other work on a secondary system :) .

 

1) set max on 1 cpu / another app on the other cpu

 

I usually try and let max have both cpu's and do something else while its rendering. If I really need to do some work, then i set max on cpu #2 with priority to realtime. (ONLY cpu2)

 

2) set max on both cpu's with affinity low / other app on both cpu's too but affinity normal

 

This works as well. However in this situation max can possibly get almost zero cpu time...where as in the above situation (max on cpu2) max still has half the system working for it.

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I've had dual processors for 4 years...

The best is to only change priorities. Let BOTH CPU's always to every app.

you can be rendering with both cpu's with one max and modeling in another max with high priority. If you set only one cpu for the rendering max.. you may loose cpu time because the other cpu is not always used 100%.

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The best is to only change priorities. Let BOTH CPU's always to every app.

you can be rendering with both cpu's with one max and modeling in another max with high priority. If you set only one cpu for the rendering max.. you may loose cpu time because the other cpu is not always used 100%.[/QB]

 

Aye...but opengl is single threaded (only one cpu), so setting that to use both cpu's wastes cycles.

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I was just stating that instead of opening up two max copies with both of them utilizing both cpu's, to open up a rendering max copy, then open up a second and set it to only use cpu 1.

 

Opengl, direct3d are single threaded. (Only use one cpu). Only if the card has SPECIFIC dual processor drivers can it utilize both cpu's. However software heidi is multithreaded (which is why it kicks some cards's ass in wireframe).

 

Like I said, the ability to set priority and affinity is just micromanagement. Everyone has their own style and optimizations. Its your computer, use it and enjoy it :) . Just don't set anything to realtime priority on cpu 1...it can cause some issues.

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