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Undervolting amd phenom ii to deal with motherboards tdp limitations

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August 17, 2012 9:14:11 PM

I got a new system which unfortunately was carelessly assembled it has a motherboard which supports cpu of 95 watt max tdp but the cpu AMD phenom ii X4 955be which is a 125 watt tdp cpu ,( I used it for a couple of weeks before I learned that) since then the machine is powered off (me being overcautious).

I was thinking about underclocking and undervolting the cpu to 2.8Ghz and 1.20 VCore voltage. Will it help,will the board survive the processor then?

system configuration:-

CM elite 311 cabinet
CM GX450W psu
ASUS M5A78LM-LX motherboard
AMD Phenom II X4 955BE processor
Power color 6770 graphics card
500 GB seagate barracuda harddisc
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August 17, 2012 9:37:20 PM

are you sure it was running at full speed at all? i would check with CPU-z if it's even going 100%
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August 17, 2012 9:56:30 PM

New system, send it back. No system builder should build a system where the cpu draws more than the motherboard is capable of delivering.
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August 17, 2012 11:06:22 PM

I did not check it for 100% load, and I dont think I will ever got to 100% I am just a casual user.
and I cant send it back now its more than a month old I got it in working condition and it runs fine even now,

I was questioning about if i underclock and undervolt the cpu ,then the cpu will be drawing less power right, and that will mean lesser TDP
Will that mean the mother board will stay alright and what are potential problems and risks in doing so.
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August 17, 2012 11:11:50 PM

What nna2 is basically asking is does it ever actually run at 3.2Ghz (regardless of load, even)?

And I actually agree with pauls3743 here. The builder should never have done something like that in first place. He obviously didn't know what he was doing, and you should definitely send it back, somehow. It's not your fault. No point in trying to fix a problem that you didn't cause (and I'm pretty sure you can't "fix" by doing what you're suggesting, anyway).
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August 17, 2012 11:25:48 PM

yes it runs at 3.2Ghz sometimes,but mostly lesser than that because of cool n quiet setting,
and I've tried doing what pauls3743 suggests before I put up the question here.
If i go for this option that will mean buying a new motherboard and replacing it myself which I will consider as a last option.

I have got my underclocking and undervolting numbers from a website eXtreme power calculator which shows the wattage to be about 85 after doing so,
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August 17, 2012 11:29:09 PM

mohdasimsayeed said:
I have got my underclocking and undervolting numbers from a website eXtreme power calculator which shows the wattage to be about 85 after doing so,


In theory, that has a chance of working, but in practice, I don't think it will actually mean anything.

Regardless, you shouldn't have even had to worry about this, and you having to do that because someone else screwed up is just not right.
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August 17, 2012 11:29:31 PM

well the socket is AM3 (aint it) So whats the surprize and thanx for the link to asus website but actually i got alarmed when i saw that page ,If it havent been for that page I wouldnt be so worried at all
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August 17, 2012 11:31:54 PM

mohdasimsayeed said:
well the socket is AM3 (aint it) So whats the surprize and thanx for the link to asus website but actually i got alarmed when i saw that page ,If it havent been for that page I wouldnt be so worried at all


Because the BIOS shouldn't even recognize it to be able to boot. Somehow, it IS recognized (or at least enough that it works), but I don't know how or why.
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August 17, 2012 11:39:32 PM

Well I agree with you. You are 100% right bios wont recognize it,

And I know its not right but i just cant argue with the system builder,
guess ill have to buy a new mother board then?

or should i try running it and replacing the mother board when it burns out,will there be a damage to the processor also
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August 17, 2012 11:45:40 PM

mohdasimsayeed said:
or should i try running it and replacing the mother board when it burns out,will there be a damage to the processor also


Since it seems to working correctly (somehow), I suppose it's ok, but I honestly don't know how using a higher TDP CPU than the board can support will affect it over time. It may be fine forever, or it may fry tomorrow. I really don't know.

The safest bet is to get a new board, yes, but man, I hate that that's the best option in all of this.
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August 17, 2012 11:51:49 PM

mohdasimsayeed said:
And I forgot to mention look take a look at this page
http://www.gigabyte.com/support-downloads/cpu-support-p...

it has three deneb(955's) one 95 watt and two 125 watt. what does that mean
and the board supports my processor and is somewhat low cost will that be okey


It just means that it will support all the 955's (unlike that Asus board, which as we know, doesn't support any at all).

But yes, that board will be fine.
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August 17, 2012 11:58:19 PM

there appears to be 2 revisions of that board, 1 that supports 95W (rev 4/5) and one that supports 140 (rev 3.1)... so keep a close eye on that if you plan to purchase it
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August 18, 2012 12:28:50 AM

Since I would be replacing the mobo,I was thinking should i try the thing I asked earlier underclock and undervolt the cpu,

What will be the best way to know if the thing worked,are there any risks other than destroying the mother board(which either way has to be replaced)
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August 18, 2012 12:37:49 AM

i suggest getting CPU-Z, if i wouldn't be suprized if it's running at 800MHz
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August 18, 2012 12:56:49 AM

yes its is running at 800Mhz
but it changes to higher values ones in a while then comes back to 800Mhz

The multiplier changes from 4 to 16 every time a new program opens and then settles down to 800Mhz with multiplier 4

why wouldn't you be surprized about what
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August 18, 2012 1:11:33 AM

well that CNQ, but is it running fine under load?
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August 18, 2012 1:18:13 AM

I havent put it under full load since i learned the build was with unsupported cpu
well it has been up for 4 hrs now temperature is 45c and Mother board temp is 42,
everthing appears fine,

but before i knew that the build was wrong i spent countless time on COD mordern warfare 3
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August 18, 2012 1:25:53 AM

Well could it be that its one of those 955 with 95watt TDP and cpu z is showing 125 watt just because it is not for my board ,

would that explain why it appears fine to me,
(well I went to the builder before i posted here and he ran the system for half an hour or so playing COD and it checked out fine thats why he refused to take back the system)
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August 18, 2012 1:28:48 AM

cod isn't a very good benchmark, they haven't updated the engine since the 3rd which was released in 2006, so it's not really a system destroyer... somthing like prime95 for half an hour would show problems, err linX as well, i get more heat output from that one
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August 18, 2012 1:34:19 AM

Okey I'll try prime95
So what is the max safe temperature for CPU and Mobo
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August 18, 2012 2:22:11 AM

61C is about tops for phenoms
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August 18, 2012 6:33:39 PM

Okey I did that,
Ran prime95 for about an hour before the cpu temp hit the 61C mark then i stopped the test, I ran it again after undervolting it to 1.20VCore and underclocking it to 2.8GHz this time it took an hour before it reached 60C and stayed there for half an hour before it reached 61C then i stopped the test.
mean while i was also looking to the tdp with HWMonitor and I noticed following:-

125 watt tdp (maximum),58 watt tdp(on average)(Without prime95 test in progress)

after i underclocked and undervolted it and ran prime95--

90watt tdp(maximum)

cpu temprature after one and a half hour 61C
mobo temperature after one and a half hour 45C

I also had words with a friend of mine who told me that he has a 125watt board and his unlocked X2 555BE (unlocked to X4 b55) reads 160 watt tdp on cpu z,still he doesnt care as he says no 160 watt mobo are available,

"Man i should ve gone for intel this tdp thing is driving me crazy"
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August 18, 2012 8:41:53 PM

how would intel help? they still have high TDP chips... and 61C isn't damaging to the chip so i wouldn't be worried about running that hot
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August 18, 2012 9:28:15 PM

So what would u recommend

and i learnt that the motherboard will shutdown the system if something goes wrong and prevent the damage to the system.

Also that i dont hear much about motherboard getting destroyed and taking the other components with them too,

this board i have, i learnt comes in three versions too,two of which support X4 955 125 watt, maybe thats how the person who build it got confused,the mobo which supports this X4 955 is M5A78LM LX PLUS(which also supports other 125 watt tdp phenoms too)

but i am stuck here i need a GO, No GO here,
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August 20, 2012 8:31:35 PM

Okey i have decided to buy a new mobo for my system in a week or two, untill then i will use this one with processor undervolted and underclocked.

Thank u all for helping me out.
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