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Prime95 AVX - Worth It Not Worth It?

SlackROG
Level 10
I've read so many conflicting things over AVX, but hey, Welcome To the Web of Disinformation Chaos! LOL 😉

1. If you're not going to use the tool and it's full potentional it's not worth it.

2. If you don't use AVX code you don't need it.

3. It damages hardware, at least it was, or suppose to of been a baddy for Haswell. Hmm Knight Rider and Hasselhoff came to mind when reading all the so called Info on Haswell. Hasselhoff Haswell, Haswell Hasselhoff, Hasselhoff Haswell... LOL

4. I don't like AVX it makes my CPU to hot.

4. AVX is not real world, nothing is going to use this, and apps like RealBench are more realistic real world usage.

Anyhow you all get the idea, go out there and look it up and you'll see over and over, this story, that story, hell, what story do you trust...

One thing I do know, I have a stable OC @ 4.7ghz 1.315v with RealBench, but on Prime 29.4b8, forget it, errors, crashes, reboots...

Oh the joys of stress testing, and trying to figure out what apps to use.

Oh almost forgot, the best I've read regarding AVX, it's because Prime95 is suppose to of undercovered a bug in Skylake regarding AVX.

What do you think about all this?
12,331 Views
16 REPLIES 16

Arne_Saknussemm
Level 40
You're not stable until you have run Prime 95 AVX for 666 hours straight...anything else is not overclocking

Menthol
Level 14
That's 666 hours in one day
Yes AVX draws more current, creates more heat, but it is part of the system
If you want your system stable no mater the load then you should test both AVX and non AVX loads, this is why there is AVX offsets so you can run at higher clocks on non AVX loads and down clock under the increased AVX load instead of running at a lower clock all the time
If you don't think you are going to run any apps that use AVX, just set an offset and hope for the best

JustinThyme
Level 13
Personally I run closer to real world and use real bench and AIDA 64

IMO Prime95= how to turn PC into space heater. Ive more than once in the past burned in 24 hours of prime 95 just to have a BSOD the first time I went to use it for practical purposes. Loop realbench stress test.....



“Two things are infinite: the universe and human stupidity, I'm not sure about the former” ~ Albert Einstein

SlackROG
Level 10
I understand a lot of this already, sorry I wasn't making any of this clear.

It's not my first time doing OC, the concerns were more about Skylake problems, and concerns of how legitimate AVX is for Stress testing, if this just goes way beyond the norm, or it's within reason, as one concern, along with the Skylake bug I mention below...

I'm pretty Geek when it comes to Linux, I compile and hack on the system and apps all the time, and I never recall anything AVX ever in my Linux systems. As far as Windows 7 is concerned, all I do is Game in it.

Also has anyone read about the Skylake Bug as it relates to AVX, this is where I'm saying, no matter what we do with our OC, or even running the system Stock, according to what I've read online, it's going to crash at some point in time;

https://www.extremetech.com/computing/220953-skylake-bug-causes-intel-chips-to-freeze-in-complex-wor...

https://www.pcworld.com/article/3021023/hardware/how-to-test-your-pc-for-the-skylake-bug.html

So there is suppose to be a BIOS fix for this, and these articles dates back to 2016.

Now when I run Prime95 at Stock for only a few minutes it does ok, run the OC for the same amount of time, and that is stable on Realbench and it crashes, which makes me wonder if it's only because of AVX I see this crash in Prime95, or the system isn't really all that stable? Of course I understand all the various stress apps respond in different ways, get one to pass and get another one to fail, and then so many different opinions on the matter...

I'm on 3504, I don't want to update to 3703, because of issues I've been hearing relating to this.

aceisme
Level 10
As far as I know, there is no AVX offset setting on this motherboard with the 6700k processor. I could be wrong, but if there is one, I would like to know about it.

Why not go down 100MHz to 4.6GHz? The sweet spot for the 6700k Skylake is 4.6GHz. The extra 100MHz is not going to give you that much better performance unless you run benchmarks all day. For what you gain, it is not worth the hassle, the extra heat, extra fan noise, extra power consumption and high CPU voltage. Power consumption on Skylake is quite linear up to 4.6GHz. Anything above that it will spike exponentially. I run my 6700K at 4.6GHz, 1.27V/adaptive, LLC-5, cache 4.6GHz, 3466 RAM and BIOS 3703 with no problems. The CPU rarely gets to 70C under full bench stress. As I type this, the cores sit between 26-30C.

SlackROG
Level 10
@aceisme I've been thinking of going Liquid Cooling, but the thought of a leak, really scares me... LOL

Yes after all my hacking I came to the same conclusion, 4.6ghz is the sweet spot, so that's what I'm going with at the moment.

I ran Prime95 for 2 hours, and temps only went as high as 75c. Most of the time they were on average around 72c-73c.

After more reading on the subject of AVX and Prime, the 6700K supports AVX2, so I think it's a good thing to stress with Prime for this, after all, who knows when you might run into something for AVX in the future... 😉

aceisme
Level 10
Yes, liquid cooling is awesome when they work. Leaks are very uncommon these days however, as far as longevity goes, nothing beats air coolers. I had a Corsair H110i-GTX that only lasted two years before I started to have issues. I think it must have started to develop some sort of blockage or something. I RMA'ed it and got the newer H115i. Apart from the name change, I don't think there is much difference between them. Corsair offers 5 year warranty on their AIOs. We'll see how long this one lasts.
Those temps on Prime95 are fine, so I wouldn't worry about it. What Vcore do you have and what LLC? You might be able to reduce the Vcore and/or LLC. Also make sure you disable MCE (ASUS MultiCore Enhancement). That will help with temps a bit.
If the 6700k supports AVX, I wonder why there are no BIOS settings to offset for AVX instructions. I know the 7700k/8700k will give you the AVX offset option in the BIOS, but with my 6700k I can't find it anywhere.

SlackROG
Level 10
I got the volts lower, I mention below, and now Prime95 ran on average 70c and hit some times only as high as 73c.

I thought they made a liquid now that is non-conductive, so if you get it a leak, it's not going to fry anything?

The Noctua NH-U14S I use runs really nice, and when I stress test, or do anything intensive, I bump the case fans up to max speed.

Air Cooling, I love it, nice and simple. I've been looking at the NH-D15 , wondering if it will give me much lower temps over the NH-U14S, but for simplicity for myself, been thinking just to add another fan to my NH-U14S, I've read I can get anywhere from possibly 2c-5c lower temps.

You beat me by .1 volts LOL... I'm now at 1.28v LLC-5, and I left ASUS MultiCore Enhancement enabled. Hmm never heard that disabling this gives lower temps?

Oh, and I've been thinking to delid the 6700K, but in the past when I did this on an Opteron, I just left the lid off, placed grease right on the chip, and then put the heatsink on it. I've seen people who are removing the lid only to regrease it, then putting the lid back on. I personally always thought the point of a delid, was to remove it and get direct contact with the chip to the heatsink, for closer contact... Hmm

aceisme
Level 10
When you delid you want to use liquid metal thermal paste, hence the reason you want to put the lid back on. Liquid metal can damage the heatsink after a while. After deliding you can expect temps to drop by 7-10C so well worth it for high OC. I don't bother with that because I'm not planning to go above 4.6GHz anyway.

Your temps look much better now so if you're happy with the performance, I would leave it as is. If one extra fan on your NH-U14S can shave off 5C, would definitely be worth doing it but I really doubt you will see that kind of reduction. The problem with an air cooler is that all that heat stays inside the case so you will need to have a high air flow, both in and out of the case. With liquid coolers, all the heat gets blown out of the case through the radiator, so your case stays cool in general. That is until the video card kicks into gear....lol