# Undervolting my Phenom II 955



## Pyrofeed (Aug 6, 2009)

So I'm more than paranoid when it come to electronics, but I am also a fiddler, not like a violinist, but I really like to mess with things. So I wondered, overclocking can potentially damage my components if done wrong, and if done right, could shorten the life of my cpu(I know this hasn't been quantified for 24/7 clocks, but its the paranoia, you know?). So I get the lightbulb. I'll undervolt! If done wrong, I restart my computer, if done right, my chip will last longer, be cooler, and more energy efficient.

I couldn't find a guide on TPU  as you can see I was distraught, but I found an oft linked to page about undervolting laptops, because I guess it is more pertinent in laptops than desktops. But they were using RMclock, which I may use, but I so far have decided against.

So I figure before I get too deep in I would post a thread on tpu for advice or warnings, but I will tell you my results so far. Btw I am doing this by software, once I get close to the limit I'll obviously go into the bios, but its easier this way.

Stock was 1.35 volts, right now I am at 1.275 volts. I've been testing with OCCT and P95. Difference in temps so far: Idle down 4c on the cpu temp, down 8c on each of the cores. Load is down 6c on the cpu temp, and down 12c on each of the cores.

I haven't hit a limit or anything, but before I go farther I would like the community's input. I haven't seen too many people undervolting with a goal in mind so I think this is an interesting project.


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## erocker (Aug 6, 2009)

There are a few threads on the subject, I don't feel like searching at the moment. AMD seems to give a generous amount of voltage for the 955's. I'm running mine at 3.4ghz 1.275v currently.


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## HalfAHertz (Aug 6, 2009)

You don't need RMClock, just use the latest amd Overdrive. It's just as good for underclocking as it is for overclocking.I would dissable C'n'Q and play around with the profiles in Overdrive


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## Pyrofeed (Aug 6, 2009)

I've been using turboV which came with my motherboard, but I'm dling overdrive right now


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## AltecV1 (Aug 6, 2009)

you have a creepy avatar HalfAHertz


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## Pyrofeed (Aug 6, 2009)

Things are still going well, any other advice?


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## Pyrofeed (Aug 6, 2009)

Ok, NOT stable at 1.25, going back to 1.2625


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## rake (Aug 6, 2009)

Tom's Hardware got theirs down to 1.175v, but it'll obviously depend on the rest of your system (yours looks bang on). When you're chasing the lower limit, you'll probably want to ensure that you dial out any vdroop before you begin.

Anyway, have a look here  and good luck!


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## Pyrofeed (Aug 6, 2009)

I keep hearing about vdroop, I honestly don't know what it is, I'll search, but can you give me a rundown? and what to do about it?


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## rake (Aug 6, 2009)

HalfAHertz said:


> I would dissable C'n'Q and play around with the profiles in Overdrive



Just be sure to re-enable it once you're done, else any energy saving will go right out the back of your case along with the hot air.


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## erocker (Aug 6, 2009)

Pyrofeed said:


> I keep hearing about vdroop, I honestly don't know what it is, I'll search, but can you give me a rundown? and what to do about it?



Explanation in all it's technical glory: http://www.thetechrepository.com/showthread.php?t=126

On every AM2+ and AM3 setup I've had (DFI LP jr 790gx, Gigabyte 770T, Asus M4A79T), I have had no vdroop.


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## rake (Aug 6, 2009)

Pyrofeed said:


> I keep hearing about vdroop, I honestly don't know what it is, I'll search, but can you give me a rundown? and what to do about it?



It's the voltage 'offset'... basically some built-in leeway. Under load you will see that your CPU core runs lower voltage than what you intended. You need to eradicate this discrepancy if you want any hopes of stability. There is another setting pertaining to CPU voltage in you BIOS where you can adjust this offset, though I'm not sure what it's called in the ASUS BIOS.

Check that article link I posted, there is a section called 'Basics of undervolting' that explains it much better than I can.


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## rake (Aug 6, 2009)

erocker said:


> Explanation in all it's technical glory: http://www.thetechrepository.com/showthread.php?t=126



Jeebus! if you'd thrown that link at me I'd have printed that article, single sided, and beaten you over the head with it!


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## erocker (Aug 6, 2009)

rake said:


> Jeebus! if you'd thrown that link at me I'd have printed that article, single sided, and beaten you over the head with it!



But don't all the nice graphs and equations help?!


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## rake (Aug 6, 2009)

They may well have driven Pyro over the edge and down into the dark abyss... and it's on your hands!


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## Pyrofeed (Aug 6, 2009)

I can't see! All the light went away after I got that falling feeling...

So now I know what droop is, but what do I do about it?

Alright, so just to clarify. I have not BSOD'd yet, but what happened was that it just restarted, is there diagnostic difference?

Is there anything else I can do to increase stability?

I mean if they got lower, I'm sure there is something I'm not doing right. I know all chips are different, but I'm sure I can get closer


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## geeman74 (Aug 6, 2009)

i used to undervolt my old amd fx55,
i used
http://users.bigpond.net.au/CPUburn/
to do it drop the voltage by then min it allowed and ran this for at least 2 hours then dropped the voltage again and ran again, did this till it wouldnt boot 
tried it with my x2 and it worked


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## Pyrofeed (Aug 7, 2009)

I feel like I'm hitting a wall...anyone else undervolt?


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## rake (Aug 7, 2009)

Pyrofeed said:


> So now I know what droop is, but what do I do about it?



Make it go away...

There are two voltage settings in your ASUS AMI BIOS: one is called 'CPU Voltage' and the other is called 'CPU VDDA Voltage'.

You must determine which of these two is the VID and which is the Offset. Perhaps some of the ASUS users here can clarify that for you.

1. Boot into your BIOS
2. Go to hardware monitor section and look for the CPU vcore readout; note the reading.
3. Go to the voltage adjustment section in BIOS
4. Set desired CPU VID (yours may be labeled differently)
5. Save and exit
6. Let the computer POST, then enter the BIOS again
7. Go to hardware monitor section and look for the CPU vcore readout; note the reading.
8. If this is lower than the value you specified in (4.) you have to adjust the Offset to a higher value.
9. Repeat these steps until the readout in your BIOS hardware Monitor matches your desired voltage.
10. Boot into OS, put some load on the cpu and monitor the vcore voltage to make sure is does not fluctuate.

Every time you drop the vcore voltage, you have to go through this process again to verify that the actual vcore matches your desired vcore.



Pyrofeed said:


> Is there anything else I can do to increase stability?



Disable 'Spread Spectrum' in your BIOS if it is not already disabled, unless you are plagued by EMI. (Note: this would be more relevant if you were doing FSB overclocking)


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## Pyrofeed (Aug 7, 2009)

What does this spread spectrum do?


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## erocker (Aug 7, 2009)

Pyrofeed said:


> What does this spread spectrum do?



Reduces electro magnetic interference. Unless you live under a cell phone tower, turn it off.


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## Pyrofeed (Aug 7, 2009)

What a coincidence, I live under the Large Hadron Collider, I think that means it stays on right? I'll try the droop and spread spectrum, and report back soon.


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## rake (Aug 8, 2009)

Pyro, if I may just respond to some of your fears mentioned in your OP...

Yes, there is certainly a risk associated with careless overclocking, but consider your own situation:
You have, by all indication, taken the trouble to put together a decent PC (properly ventilated case, stable power, reliable motherboard). In addition, you bought a Black Edition processor, which allows you to overclock just your CPU through multiplier increases and not necessarily your whole FSB.

Thus I see no detriment to exploring mild CPU overclocking, done at stock voltages. I have found that the stock AMD cooler on my X3 720BE was more than able to cope with 4 cores running at 3.2GHz and was even able to run completely stable at slightly less than stock voltage.

So, should I stick to 2.8GHz just because AMD has to play it safe when they produce a processor that may well end up in Joe Soap's asphyxiated rig with a side order of cable salad and wobbly 12v rail sauce?

At the end of the day, you have to wonder who's processor will last longer.

If you have invested in quality components, you almost owe it to yourself to tweak them into maximum efficiency (not necessarily maximum speed).

Just some points to ponder next time you get a paranoia attack


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## Pyrofeed (Aug 8, 2009)

Thanks for the encouragement rake, I still don't know much about overclocking, and my undervolting adventure is actaully being somewhat educational on that front, without the risk of screwing up, I may overclock, but I still don't know enough about it.

Some suggestions I've found so far to help me drop voltage and temps and get more stable
1. Drop the HT Link- Tryed it, seems to make it more stable, but I had to lower it all the way to  achieve that

2. Drop the Cpu multiplier and voltage, and compensate with the System clock- Have not tryed yet because I know it will jump my ram and I don't know how to change the ratio in my bios

3. A burn-in on a somewhat stable voltage- Have not tryed yet, may attempt when all other methods exhaust themselves


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## hippie (Aug 10, 2009)

*My 940 experiences*

My reasons for undervolting were to tame the heat my 940 BE was throwing out. I went from an Artic cooler 64 to a Core contact and still at stock 1.35@3ghz this guy would go over the 62c max core temp while running LinX (this heated my system up more than OCCT for some reason!) 

After reading a bunch I found this little progam PhenomMsrTweaker 

I liked its cleaner interface and ability to run as a service on startup. First I bumped the voltage down to 1.25 from 1.35 and ran LinX or OCCT for about 30min. If it passed that w/o errors I started bumping it down one notch at a time and testing. I got down to 1.2250 and hit a brick wall. After about 3hrs of gaming or 20min of stressing I'd BSOD. 

So I took another step. I bumped 2 of my cores down to 2.9ghz and worked my way down to 1.20 where im just sitting atm. 

I have my P1 state (power saving) is .950v @ 1.8ghz
P0 state (performance) 1.200v w/ 2 cores 3ghz other two 2.9ghz. 

I can't wait until the winter comes and I can bump my volts back up  

I hope I made sense and this helps. Also, I disabled CE1 and Cool N' Quiet. I enabled ACC on all cores (auto). If you have BIOS option question our boards are probably pretty similar I let you know what setting I have.

Oh! And for my P1 I did it the opposite, I started with .850v @ 800mhz (lowest possible) and pushed the multi up one notch at a time until i'd blue screen, when I did I'd move my volts up a notch. My goal from this angle was I was upgrading from a x2 45w processor and wanted to find the lowest power I could make my 940 sip and still be the same or better performance than my previous chip.


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## farlex85 (Aug 10, 2009)

I generally try to undervolt and overclock simultaneously if possible. I'm sure it's a bit different on the intel side though, I haven't dabbled in PII so I can't fully relate. I OC'd my Q9550 to 3.65ghz though (from 2.83) and undervolted to about 1.2v (1.26 VID I think) and it was stable, but my mb doesn't like to restart properly if it's not happy, so I bumped it up to 1.22 or so. I leave on all the throttling, so that goes as low as 1.15 and really on account of vdroop doesn't go any higher than 1.19v or so. 

To me undervolting isn't really worth it unless you can get some extra clock out of it too.


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## hippie (Aug 10, 2009)

*Impressive!*

Thats a nice over clock you have going there, with the lower volts. Wish my 940 could pull 1.18v@3.6ghz


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## farlex85 (Aug 10, 2009)

hippie said:


> Thats a nice over clock you have going there, with the lower volts. Wish my 940 could pull 1.18v@3.6ghz



Thanks, I wish I could test it further, cuz I'd wager it could go a bit higher w/ a bit less volts than VID, unfortunately my board doesn't let me push the FSB for this thing much higher.


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## mudkip (Aug 10, 2009)

erfwrf4


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## rake (Aug 10, 2009)

Pyrofeed said:


> Is there anything else I can do to increase stability?
> 
> I mean if they got lower, I'm sure there is something I'm not doing right. I know all chips are different, but I'm sure I can get closer



Ah yes, something I completely neglected to mention: *ACC* (Advanced Clock Calibration). Be sure to enable it in your BIOS. While AMD have been very tight lipped about how exactly ACC works, it has been proven (by Anandtech and others) that it improves OC ability for Phenom processors, moreso if you happen to be stuck with a bad apple.

Supposedly it can help with undervolting as well.

Just set it to 'AUTO' for now. Later on, if it turns out that you have one wonky core, you can mess about with individual settings. (I'm still experimenting with those)


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## Pyrofeed (Sep 1, 2009)

I'll check it out, I don't know how much lower I can really go, I'm happy with 2.625 but I would like lower


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## Velvet Wafer (Sep 2, 2009)

hippie said:


> Thats a nice over clock you have going there, with the lower volts. Wish my 940 could pull 1.18v@3.6ghz



my 955 did 3.2 at 1.2. not too bad ;-)


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## Pyrofeed (Sep 12, 2009)

So the ACC seems to help, I can not for the life of me find an explanation as to why, but its doing the job. I'm steadily dropping, I'll post back when I find a new low


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