Author Topic: xeon v4 cpus  (Read 43790 times)

2016-06-30, 13:19:39
Reply #45

Juraj

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What abou the AVX instructions ? Is that something that has to be tweaked by bios or can Corona do something ?

My IvyBridge v2 Xeons, run at 100perc, full all-core turbo.

My Broadwell v4 Xeons, run at 95perc (all of them), and underclock even bellow the base clock (like negative all-core turbo heh). What's up with this ? That's more than 5-7 perc. loss of performance. Funky.
(this is only with Corona benchmark, other benchmarks run at 100perc. and correct turbo clocks).

But if I compare the rations between this benchmark and Cinebench, they are pretty similar...which leads me to question if it's only potential loss. So the AVX instructions are faster, thus don't need to run that high clock to provide identical performance.
But if that is how it works, why even bother introducing them ? To run at lower TDP ? There is no actual performance gain.

I don't get Intel, they fail to introduce any meaningful performance upgrade. V4 are only faster because of massive core count, but the per-core improvement is zero. The difference between v1 SandyBridge-E and v4 Broadwell-E is almost non-existent.
Quite a failure compared to the GPU improvements.
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2016-06-30, 19:02:29
Reply #46

Juraj

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Would it not be possible to compile non-AVX Corona benchmark ? Based on every reading, AVX does run on lower clock to fit within given termal limit, but it should still be faster overall. From my comparisons, it doesn't seem at all. Seems to be either the same, or little bit (2-4perc. slower). I guess I am asking for either stupid or impossible thing :- ) But my curiosity runs amok.

I now stand educated that there is such thing as AVX an non-AVX base clock, and AVX and non-AVX turbo bins. Like it wasn't complicated enough that Intel has 20 public and 10 OEM versions of CPU in each generation of Xeons family :- )

« Last Edit: 2016-06-30, 19:43:44 by Juraj_Talcik »
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2016-06-30, 20:52:22
Reply #47

Ryuu

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Would it not be possible to compile non-AVX Corona benchmark ?

We already talked about this with Ondra. We'll try to prepare something if there's time. The problem is that even if we have a non-AVX version of Corona, there can still be some AVX code executed from within the standard library, OS or even some other application scheduled on the same core. All it takes is just 1 AVX instruction executed each millisecond to keep the AVX execution unit powered up.

2016-06-30, 21:01:22
Reply #48

Juraj

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I see. But since v4 can (as you wrote too) 'limit' only those cores that use AVX, it would still be interesting to see.

I thought that Vray would execute same behavior given they use Embree as default now too, but it didn't, so I presume they don't use AVX for it.
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2016-06-30, 21:03:57
Reply #49

Juraj

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For the others issues (if anyone is waiting), I am currently installing all Windows I have (7 enterprise, 10 pro, and Windows2012 server, might even try the 2016 beta), to see how each behaves.

The runtime broker in this cause is connected with the search function, that, and that only. But I've been trying for hours today to fix it, re-registering it,etc... to no avail. It's odd, can't for world see how it connects to existence of processor groups, but somehow, it does.

There is no newer bios for Asus boards also. It is strange, because the current one is from December, yet Asus has in marked as March '16 (when v4 came out), but it is the very same and I even tried overwritting it, it worked, but it indeed was the same.
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2016-06-30, 21:25:05
Reply #50

GabaCGStudio

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SSI-CEB. It aligns with E-Atx you just put away the standoffs that don't match (two of them).

Thanks for your reply ...

but two fans with one kilo weight (two kilos) in tower case?!?! i believe that the rackmount 4U case will be better for this config.
« Last Edit: 2016-06-30, 21:32:43 by GabaCGStudio »

2016-06-30, 21:27:20
Reply #51

alexyork

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SSI-CEB. It aligns with E-Atx you just put away the standoffs that don't match (two of them).

Tanks for your reply ...

but two fans with one kilo weight (two kilos) in tower case?!?! i believe that the rackmount case will be better for this config.

It's honestly fine. All our workstations are basically this exact spec and are rock-solid.
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2016-06-30, 21:41:40
Reply #52

Juraj

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but two fans with one kilo weight (two kilos) in tower case?!?! i believe that the rackmount 4U case will be better for this config.

Believe whatever you want, you're buying the case :- )
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2016-06-30, 22:50:18
Reply #53

Nejc Kilar

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SSI-CEB. It aligns with E-Atx you just put away the standoffs that don't match (two of them).

Thanks for your reply ...

but two fans with one kilo weight (two kilos) in tower case?!?! i believe that the rackmount 4U case will be better for this config.

Just want to put it out there in case someone doesn't know... While SSI-CEB is compatible with E-ATX (going by your word, I didn't check the compatibility list), SSI-EEB is not! If you have a SSI-EEB motherboard you need to buy a case that supports E-ATX + SSI-EEB.

Might be a total given to all the techies here but I reckon it is not like that for everyone...

Peace!

2016-06-30, 22:57:04
Reply #54

GabaCGStudio

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Z10PE-D16 WS is EEB platform ... not CEB ...

2016-06-30, 23:39:32
Reply #55

Nejc Kilar

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You've got good eye if thats the case! There are actually cases (computer chassis) that support both standards, you just need to move the standoffs appropriately. A lot of the cases however are E-ATX but have no support for SSI-EEB. You need to be careful to double check if it really supports that particular standard.

I am unsure how things are with SSI-CEB with regards to it being supported on E-ATX cases. Based on my quick research I think if you have an E-ATX case then you are cool with having a SSI-CEB board.

2016-07-01, 09:21:20
Reply #56

Ondra

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Is it possible to disable AVX in bios? Just curious... ;)
Rendering is magic.
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2016-07-01, 11:05:10
Reply #57

Juraj

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Is it possible to disable AVX in bios? Just curious... ;)

I don't think so, I searched everywhere :- ). Neither to se the clocks for it.
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2016-07-02, 09:24:22
Reply #58

Ryuu

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I tried building a few testing versions of Corona with different (non-)AVX settings, but it is just as Ondra predicted, there are always some AVX instructions used in the compiler runtime library (which is completely out of our control).

From my point of view, there are only two solutions to this problem:

  • Switching to a different compiler - This would probably have to be an older version of Visual Studio (2010?), which is something we really don't want to do.
  • Taking full advantage of the AVX(2) instruction set - Right now there is no AVX explicitly used in Corona itself and the compiler is apparently unable to take full advantage of this instruction set even with appropriate settings. This means that we would have to code AVX optimizations by hand. It would be relatively easy to do this for code like texture loading or denoising, but the rendering core itself is a whole different beast.

I'm afraid there is very little we can do at this moment. I'm always happy to rewrite any part of the code to optimize it, but this would mean much bigger changes than what we are able to do at this point. I'll definitely keep searching for other solutions.

2016-07-02, 11:04:00
Reply #59

Juraj

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It's extremely little issue, I doubt there is a lot of people with Broadwell-E E5 Xeons, and we loose just marginal performance. It was still educating to learn this.

Cool that you had looked into this.
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