I am a proud new owner of an FX-8350, but I have a problem. It is clocked at 4.0 GHz at 1.3375V, which are the default settings on my board. I was running Prime95 on Small FFTs to check out baseline temps and I am getting errors. I am getting
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FATAL ERROR: Rounding was 0.5, expected less than 0.4
Canis-X Forum Moderator
Posts: 693
Joined: 08/28/2012
It's not the CPU man...Since you didn't list your power supply I can't really say that it could be the cause but I can definitely say that your motherboard is...you bought a very power hungry CPU and you decided to place it on a very power weak motherboard (4+1 phase count)....this in an of itself is not neccessarily a bad thing but then you expect it to not error out while pegged near 100% load on all 8 cores!?!?!?!? That is just an insane concept....read below....
Failures on motherboards with higher phase counts have been relatively infrequent if at all. Most of the culprits for VRM failures are the lower end 4+1 phase and 3+1 phase motherboards that aren't equipped to handle processors that consume lots of power and may be overclocked. Smaller 4+1 phase systems or less on CPUs can be particularly risky due to the fact that each transistor must be capable of outputting more current and heat. This is why you normally see motherboards with low phase count failing (i.e. catching fire, frying, overloading), often on motherboards from only certain manufacturers or certain particular motherboards.
However, the motherboard brand/maker and their quality control can also define the quality of a VRM system. For example, the majority of 2010-released MSI AMD motherboards with 4+1 phase or similar, heatsinked or not, did not have good quality and were prone to failure. This was due to the utilisation of transistors that may not be properly rated, driver chips not properly rated, and lack of VRM over-current protection. However, the Biostar TA890FXE, which comes with a similar-sized 4+2 power phase, was not failure-prone. It featured high amperage rating per transistor; completely rock-solid.
An 8+2 phase system may not necessarily provide any more current than a 4+1 phase if the amount of amperge capacity throghout the VRM system is the same; however, the 8+2 phase system would still do so with more efficiency, stability, and with less heat output. The situation of power phase count can be summarized in the following two sentences (in case the above was too long and complicated for you) by OCN PSU editor Phaedrus2129: Quote: Originally Posted by Phaedrus1219 However, as a practical consideration, many VRMs with more phases can supply more power. I mean, assuming you want to output 64A, it's usually cheaper to use sixteen 8A transistors than four 32A transistors. So more phases makes it cheaper to make the VRM more powerful (usually). So a VRM with fewer phases will often (but NOT ALWAYS) be less powerful, since making it more powerful is more expensive.
Moral of the story is, you can have the strongest CPU in the world, but it you don't supply it the power it doesn't do you a lick of good......another analogy.....your rig is only as strong as it's weakest component.
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The opinions expressed above do not represent those of Advanced Micro Devices or any of their affiliates. Requiescat In Pace AMD Processor Forums | Member since: 1/19/2009 | Post count: 4142 Please don't PM me with questions, instead create a thread so that everyone can assist and benefit from the knowledge provided. Thanks in advance!
Oh, wow. Thanks for the replies. I've never heard of this phase thing before. Previous to this I had a Phenom 2 X4 and had it overclocked on a really cheap board. I never even thought that the board could be a weak point supplyign power. My PSU is an X-Power 650W. I am still concerned, however, that the same threads are failing every time I test them.
Also, to Black Zion, I am running it because I planned to push the clock speeds a bit and wanted to ensure baseline performance (which seems to have been a good idea).
QB the Slayer Grinding Levels
Posts: 140
Joined: 11/27/2012
Unless you have LLC in your BIOS, 1.375 VCore is not going to cut the mustard... There is a massive V-Droop with these CPU's. A good way to see this in action is to run OCCT and monitor the voltages when under load.
black_zion Heavy Wizardry
Posts: 9874
Joined: 04/17/2008
No Caesar, you shouldn't run Prime95 unless you A) have a quality motherboard (as Canis mentioned) and B) an aftermarket cooler which is required for overclocking anyway.
I do have an aftermarket cooler. I overclocked my last processor from 3 -> 3,5 GHZ, and it ran stable. So I'm not entirely new to the game, but I never had a motherbord be the (obivous) weak point point before. Look slike I have a lot of reading to do.
black_zion Heavy Wizardry
Posts: 9874
Joined: 04/17/2008
It's all to do with the power. QB pointed out the voltage droop, an 8 phase power supply system helps counter it as well as providing a "cleaner" power signal (more stable). Most motherboards have an option to increase Vcore under load to counter the droop as well. And if course there is the power supply, if the +12v rail drops below 11.9v you're in trouble. But yea, overclocking should never be done on a lower end x70 or x60 motherboard, since they are usually built down to a price and lack cooling and lack the higher quality components of the higher end boards.
Prime95 should also be taken in context as well, as I've had overclocks that wouldn't pass Primce95 for a minute yet I could hammer it with video or audio encoding and it wouldn't miss a beat.
Mime Forum Moderator
Posts: 503
Joined: 08/28/2012
That's the "elephant in the living room" kind of stress testing.
If it passes all the tests I care about, but fails on the others, then the others must be wrong and bad, somehow... I guess... or something.
Prime95 is computing known values while running the torture test, so any variance from the known results indicates a problem. If you can beat the hell out of the machine with some other apps and not see a problem, then good for you, but you still have an unstable machine on your hands. Whether or not you care enough to fix those rare cases where the machine could scream and die is a different question.
Anyway... bad CPUs are usually an all-or-nothing kind of thing. Either they're completely fine, or completely dead. To have one still work but be the cause of crashes and other problems is rare. Check the board and PSU, as others said above... those are much more likely culprits.
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Do not meddle in the affairs of archers, for they are subtle and quick to anger. Post Count: +8510 Troll Hunter
The opinions expressed above do not represent those of Advanced Micro Devices or any of their affiliates.
I decided to return my motherboard and get a better one. Thanks for the input everyone, this is my first time running into power issues. I have learned a lot.
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02/06/2013 06:07 PM
