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Burn in CPU or dont waste time?
Old 27 December 2011, 00:21   #1
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Hey guys,

So is a "burn-in" really necessary? Been trying to do a research and am starting to edge towards no but wanted to get your opinions on the subject.

Now im gonna base this on fact and not "what some guy once told me" sort of thing.

Why "burn-in" Well the only real reasons I can see are
1. Certain thermal materials need thermal cycles to cure.
and
2. To test for stability.

Beyond that I see no reason, and even then reason 2 is subject to debate as I know they stress thest these in the factory before sending them out the door.

The one 'argument' and I use that term loosely, I keep seeing is that its like a new car motor and you need to break it in, this isnt a car motor, there are no mechanical parts that need to be worn in so that sort of falls flat on its face.

The only other argument Ive seen is that it "prevents throttling" whatever that means, I dont see how it could do anything of the sort.

So what do you guys think? Burn-in or not waste time?
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Old 27 December 2011, 01:42   #2
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CPU Burn-ins are really useful. CPU Overclockers use and should do burn-ins to test, like you found out, stability.

Its kinda like running a game that's graphically intense after you have overclocked your video card to test for artifacts.
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Old 27 December 2011, 02:16   #3
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Yes to test stability you should definitely stress test but a burn in and a stress test are different(ok the method is the same), some people think you need to do a burn-in on a new cpu to somehow make it better, I see no scientific reason why though.
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Old 27 December 2011, 03:21   #4
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I got the feeling that your processor already had been "burned in" at the class test stage of manufacture to find the top speed/core reliability. Here is a quote about it and a link to Intels rough stages.

Does Intel test their silicon on the wafer or after the cores are cut out?
Both.

Do they use a set voltage and ramp up clockspeed to a failure of some sort?
Sort of - there are various test points. A test program which sets up the voltage and ramps up either voltage or frequency or both is called a shmoo (don't ask... that's the name http://en.wikipedia.org/wiki/Shmoo_plot). They take a while to run and testers are expensive and fast testing programs are created which hit the main areas quickly without testing the intermediate points and this is a lot faster than doing shmoos.

Do they test at various voltages and frequencies?
Yes.

What type of application do they use to test silicon?
All of them and none of them. This is a complicated topic, but the tests on the testers aren't actual applications - they are snippets of applications. In the creation of the test programs, engineers figure out what the worst applications are and essentially try to write those massive programs as much shorter tests. This is harder than it sounds. Also using design knowledge - designers know what the worst conditions for their units are - you can write hand-coded assembly that often does better than real applications at testing a unit's function. So the testers don't run real applications - they are running abstractions of real applications.

How long does the test take?
Less than 1 second usually.

Do they test the max clockspeed of each core?
Yes.

For an overview, the first step after fabrication is called sort. It's a wafer test that tests the full wafer. It's done at speed to some extent but power-delivery is an issue so it's not a full power test. Checks are done on the cache, and as many transistors as possible are tested to make sure that they can toggle on/off. Then the parts are packaged and they go to "class" testing which is done at multiple temperatures and voltages and they are binned and fused. Then they go to burn-in testing which is an accelerated stress test environment designed to weed out early failures. Then back to class for post burn-in binning and then they are shipped.

There's a pretty graphical overview of this here:
http://download.intel.com/pressroom/..._of_a_Chip.pdf (Adobe PDF)

See pages 10, 11 and 12. They skip burn-in but otherwise it's a good high level overview... with cool pictures.

Patrick Mahoney
Senior Design Engineer
Intel Corp.
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Old 27 December 2011, 04:14   #5
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lyla, I knew they went through all that(I assume AMD follows similar procedures) and thats why I dont see the need for a burn-in like some people seem to think they need, maybe run prime95 fore a few to make sure its all stable but there is no need to run it for hours and hours.

Just wanted to get everyones thoughts, I think the whole "you need to burn-in a new CPU" thing is just a myth with no valid backing.
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Old 27 December 2011, 05:56   #6
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I usually use AMD OverDrive to test my OC, but i found that running PCSX2 (PS2 Emu) will find waaaay faster a bad OC than most applications, when i do a bad OC the emu would crash in the first 5-10 minutes while AMD OverDrive and Prime95 takes even up to 2 hours to tell me i did a bad OC... haha, got to love PCSX2 for that.
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Old 27 December 2011, 06:15   #7
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What I do is just run prime95 for about 30 minutes and if it doesnt fail then I just go on using the computer, if I start getting BSODs or application crashes then I know its not stable and tweak it again, just never feel like sitting there for hours and waiting, such a waste of time.
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Old 27 December 2011, 09:05   #8
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Quote:
Originally Posted by blindartist View Post
maybe run prime95 fore a few to make sure its all stable but there is no need to run it for hours and hours.
From my experience, problems surface after a few minutes of stress testing. Giving it a few hours is enough if you ask me.
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Old 27 December 2011, 17:11   #9
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Old 27 December 2011, 23:33   #10
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Yeah, I agree with your two reasons for CPU burn in blindartist. I leave my computer running overnight when doing a stress test, but only if I know the cooling system is good enough. Ah! Another reason for CPU burn in is to test your cooling system, duh...
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