Dual Processor..

mikeblas

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Leright said:
yes....so what is your point?

My point is that a thread might run on more than one CPU, but not run on more than one CPU at the same time. If it has no affinity preventing it from doing so, a single thread might "use both proessors"; it just won't do so concurrently.

What's your point?

.B ekiM
 

Leright

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mikeblas said:
My point is that a thread might run on more than one CPU, but not run on more than one CPU at the same time. If it has no affinity preventing it from doing so, a single thread might "use both proessors"; it just won't do so concurrently.

What's your point?

.B ekiM

Thanks for the input, but I think it was clear we were discussing that a thread cvan't use both processors concurrently.
 
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AMDXPCottonFire22 said:
Excuse my nubbish but exactly what benifts does a dual processor have? For example if its dual 2600+ amds does that make it like a 4000+ ? even though it operates at 2.0 ghz each processor?

Are dual processors worth it?

The explanation that I standardly use to explain dual processors to a novice:

Think of a one-lane freeway. There's a sign there that says "Speed limit 2600" (since you're talking about 2600's). Install a dual board. Now you have a two-lane freeway, it still has the same "Speed limit 2600" sign.

You won't get there any faster on the dual board than on the single. However, under heavy load it won't slow nearly as much.

I can run compute-heavy things in the background without affecting the system's response noticeably. (And if the second task were pure computation with no HD access there would be no effect to speak of.)
 

gnewbury

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Tim_axe said:
I guess this can be filed under something like "Win2K not the best multiprocessor os", etc., but I'd like to mention this and maybe gain some insight into what it happening.

I don't know the correct name -- thread, process, some task, etc -- but Win2K tries to balance a program across the two processors. It does hurt performance, so I have to set processor affinity, etc, to correct it. But I'll post a screen capture demonstrating this, although I don't quite know what it means other than it sucks for performance.


1 instance of F@H with processor affinity to "both" processors (default). It "load balances" or something, and generally hurts performance...especially when two instances do this horrible act...
What is "this horrible act" ?
When I run two processes cpu usage is maxed out, except for the time of the faulty doubleG.
1 instance generally uses 50% plus on CPU usage with most on 1 CPU and then a little on the other, as below. No affinity assigned.
cpu1.gif
 

Tim_axe

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When I was first playing with my new dual rig, Folding@Home was juggled by both processors fairly evenly, making the usage graph I posted earlier.

I don't like a thread to move onto different processors to find that its L2 data is missing, and then going to retrieve it over a shared 133MHz (266MHz bandwidth) bus. And then some time after doing this, moving onto the other processor to repeat this again. Although I'm sure this happens all of the time in the uni-processor world, I am concerned about my machine doing this with its somewhat higher latencies and lower bandwidth (and having both processors share this together). If I had a dual Opertron machine with 800MHz HT (or maybe even a 533MHz bus Xeon) and some low latency memory, I'd guess it wouldn't be something to worry about, but on my slower and higher latency 760MPX I'm worried that my processor is going to be waiting on getting data to its L2/L1 so it can get to work. Granted, I don't have more than 4 processes begging for a ton of CPU time so my concerns may be taking an extreme stand, but I still feel that it hurts performance (even if I can't see it) to wait on a slow memory system (compared to 800MHz HT links, etc) to deliver data to the processor to be processed.
 

relic

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Don't sweat it Tim. Quite a few of us tested setting the processor affinity in F@H.
It never made much difference. I suggest firing up a second copy of f@h (check out the DC forum for the proper settings) and keeping both those CPUs nice ans cozy warm. ;)
 

mikeblas

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gnewbury said:
When I run two processes cpu usage is maxed out, except for the time of the faulty doubleG.

What is the "faulty doubleG"?

Is the source for Folding at Home made available? I poked around at folding.stanford.edu, but I couldn't quickly find a source code download.

.B ekiM
 

mikeblas

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Loren Pechtel said:
I can run compute-heavy things in the background without affecting the system's response noticeably. (And if the second task were pure computation with no HD access there would be no effect to speak of.)

If you (or the programs that you run) set process priority correctly, you can do this on a single-proc box. I run DNETC on single-proc machines all the time, and there's no way to tell it is there. That's because it sets a low priority for itself, and doesn't get time when anything else that's of a higher priotiy needs to be done.

.B ekiM
 
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M11 said:
Very true.

Right now I a running dual opteon 244s on a MSI K8T-Master2, and have been very pleased with the performance. As was stated earlier, they do not add in a mathematical sense but rather they compliment each other through simultaneous thread execution. This lets me have a limitless number of windows (2GB RAM, I still have not found the upper limit on simultaneous apps), and even play UT2K3 while burning 2 DVDs at once:D

Man if you can do all that, I might have to build me a system. Are there any dual processor boards that support PCI-express yet?
 

zoom314

Limp Gawd
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touchless21 said:
Man if you can do all that, I might have to build me a system. Are there any dual processor boards that support PCI-express yet?

Yeah, But It's an Iwill DK8E2 and It uses the nForce3 250/Pro chipset, but It isn't out quite yet. It does feature 2 PCI-E video slots though. But If You want to overclock, Forget It, None that I know of for one reason or another will do It, On the nForce3 250/Pro It's Chipset Limited cause of having 2 cpus and was Limited by nVidia. Here is a picture of one, enjoy.

willy1.jpg
 

dagamore

Gawd
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touchless21 said:
Man if you can do all that, I might have to build me a system. Are there any dual processor boards that support PCI-express yet?

all intel boards based on the 7520 and the 7525 boards have atleast one pci-Ex and most have 2 PCI-Ex but none of them have any AGP support, also they support the new 800mhz fsb xeons :D very fast, very smoth, and not too expensive.
 
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