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Author Topic: Most powerful computer possible for a reasonable price  (Read 5963 times)
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stardust4ever
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« Reply #60 on: May 07, 2012, 08:12:01 AM »

That is very nice. Tons of fans LOL! Does your computer sound like a race car engine, or are they throttled? With all of those giant fans, it should be possible at least to run the external fans at 5V and keep everything cool. And the motherboard should be able to throttle the CPU fans if they are 4-pin smart type. What size are your CPU cooler fans? They've got a similar tower design compared to my CPU cooler, but mine's only got one 92mm fan on it though it could easily accommodate two.

One-half the speed with four times the cores equals twice the muscle. Your big rig PC can haul more @$$ than my sports car PC can. It's a shame you can't overclock an Opteron processor though. I'd imagine that the cores are capable enough to go up to at least to 3Ghz without instability. Like I said before, I run mine on max turbo, but I guess yours would be like running the engine at red-line continuously: you'll need a seriously big radiator to keep it from overheating!
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Dinkydau
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« Reply #61 on: May 07, 2012, 09:02:07 PM »

The computer is very silent with the fans not on full speed. The first time I even thought it had shut down when I came back in the room. I couldn't even hear it because of my footsteps. My previous computer was extremely loud, so I did everything to prevent that this time. The case has one 140mm fan on the back and three 230mm fans in total, on the front, side and top. The CPU coolers have 92mm fans.

In the meantime I've found out that while using fractal extreme all cores are at 2,1 GHz. While using apophysis (which uses floating-point operations), the cores go to 2,4 GHz, while task manager and open hardware monitor report all 32 cores as 100% loaded. I think the OS is confused by this weird architecture.
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Dinkydau
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« Reply #62 on: May 08, 2012, 12:21:03 AM »

16 GB is more than enough. What would you use 64 GB for?
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Dinkydau
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« Reply #63 on: May 08, 2012, 01:31:35 AM »

@stardust4ever, your idea of setting the affinity in task manager to CPU #0, #2, #4 etc. skipping one CPU each time for floating-point programs works well in apophysis. Although it multithreads really badly, the render time varied between 85 hours and 124 for this particular render using 8 threads. 85 Hours with your method, 93 with all 32 cores available, 124 with it restricted to 4 modules (CPU #0 trough #7 without skipping any).
« Last Edit: May 08, 2012, 01:33:26 AM by Dinkydau » Logged

stardust4ever
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« Reply #64 on: May 08, 2012, 03:40:47 AM »

In Windows 7 Pro 64-bit with FX-8150, based on my own original research, each module contains two cores spaced 4 units apart. In other words, (0,4) share a module, and so on.

(0,4)(1,5)(2,6)(3,7)

I imagine other combinations of Bulldozer processors and operating systems may be enumerated differently. You'll have to experiment with different bit patterns and see which is fastest. With fractal Extreme, setting affinity to (0,1,2,3) or (4,5,6,7) is about 20% faster than setting all evens or all odds, so that is where I get my info. They may very well enumerate differently on your dual Opterons. Also, Microsoft still has not released the microcode update patch for the Bulldozer platform, so Windows 7 will not yet perform load-leveling optimization by threading empty modules first like it knows to do for Intel's hyper-threads. That is one highly plausible reason why Intel's charts are currently further ahead than they should be in benchmarks. If you have a program that only uses 16 out of 32 available threads, it may be beneficial to arrange them so that each thread gets it's own module, or else they will randomly collide by filling up some modules and leaving others vacant. The performance penalty will be especially significant with floating point operations.
« Last Edit: May 08, 2012, 03:44:25 AM by stardust4ever » Logged
Dinkydau
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« Reply #65 on: May 08, 2012, 04:29:16 PM »


Oh yeah, now that you mention it, your pattern was actually different. With my CPUs, apparently it's (0,1)(2,3)(4,5)(6,7)(8,9)(10,11)(12,13)(14,15). There are still some things that are a little weird. I've tried almost every combination possible and skipping one core each time appears to be the most effective. Here are some render times for a very heavy fractal that (for apophysis) multithreads well, with different CPU affinity:

1 thread, 4900 hours


16 threads, 400 hours


16 threads, 393 hours


16 threads, 368 hours


16 threads, 332 hours


16 threads, 323 hours


16 threads, 323 hours


32 threads, 222 hours


1 Thread takes 4900 hours, 16 threads in the most efficient configuration takes 323 hours:
4900 / 323 ≈ 15,17 times faster, which is good.
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Dinkydau
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« Reply #66 on: May 19, 2012, 09:19:20 AM »

In case anyone is interested, I made what was going to be a small presentation of the computer.
<a href="http://www.youtube.com/v/Vcl38JXg2T0&rel=1&fs=1&hd=1" target="_blank">http://www.youtube.com/v/Vcl38JXg2T0&rel=1&fs=1&hd=1</a>
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