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View Full Version : CPU type and MR results


LemonNado
06-19-2006, 06:29 PM
When different CPU's are used within a satellite rendering environent, is it correct to expect different results because the FPU's might come up with slightly different results, or does MR compensate for that and returns the correct results in any case and regardless of CPU?
Cheers
Rainer

Waz
06-19-2006, 07:25 PM
I believe it does, in my render farm setup at home I have a mix of AMD and Intel platforms and havenít run into any problems. In 3ds Max I ran into problems though as you could tell which cpu rendered which square using finalrender.

LemonNado
06-20-2006, 09:26 AM
We evaluated Final Render for C4D a week ago.... MR rulez!
Rainer

Eismann
06-20-2006, 12:03 PM
Even though numerous sources (including softimage officials) claim that there are no differences in MR rendering between Xeon/Opteron, there are.

We encountered them in various projects.

So we split up our rendering to be either Intel or AMD and never mix.

Greetings,
E.

AdrianLazar
06-20-2006, 03:00 PM
Eismann, wich one is better? :scream:

Freak!!
06-20-2006, 05:55 PM
No it doesn't compensate automatically, for Rounding Errors, introduced by certain CPU types.
It's most common in procedural elements or particle type fx.

Has anyone tried XSI 64 for comparison?

The 64bit processers from Intel and AMD are meant to be a bit smarter at maths, (larger registers) to help aleviate this kind of problem from occuring.

Theoretically, 64bit processers should give similar if not exact same results.
(I'd like it confirmed though)

LemonNado
06-20-2006, 06:20 PM
Dang... no free lunch....
However, AMD is faster in the Math Department. Both have valid results. It's the rounding which makes the difference in the output. If no floating point would be used the problem would not be apparent. Darn flopps...
Rainer

AdrianLazar
06-20-2006, 06:23 PM
pppffffiu... so i made the right decision, i had to choose between 2xdual core amd opteron 64@2ghz and 2xIntel xeon... now i`m wayting the system to arrive for hardcore testing!

DragonslayerAz
06-20-2006, 08:47 PM
Hey y'all.

In the experience that we've had here at work with our render farm, I can only say the following.

There seems not to be a difference between the perfomance of Intel processors, whether dual Xeon CPUs or the single-processor (Celeron) type, even when throwing Intel's Dual Core processors into the mix, that isn't the speed at which the frames are rendered.
We've done HD renders (pretty complex renders, while at it) a few times by now, and I can tell you that there isn't anything noticeable as far as the image's quality goes.

What left us dazzled was the speed of dual core processors.

When we added the last CPU to the render farm, which has a single Intel Core Duo running at 2.16 GHz, it rendered almost as fast as a CPU with dual Xeon 3.2 MHz processors installed on it.

As far as AMD processors goes, I just can't tell. I've never owned a computer with an AMD processor, nor have I used one with applications as demanding as XSI or Combustion, for that matter.
But, considering the results I've seen so far, I don't think I'd switch to AMD.

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