I just built a uATX system for a friend and he did not want to overclock it but he did want to undervolt it. I put it down to 1.25v from 1.35v and it ran totally stable, I didn't bother going lower as the temps hovered just under 50 deg but just thought I'd ask and see what the lowest v achieved at 3.0Ghz on a 940 is. If it is significantly less I may go lower just to entertain myself.
Undervolting Ph II 940, what is your lowest stable voltage?
- Thread starter deputc26
- Start date
I'm probably getting one next week and I value low power consumption as well but I will be underclocking as well. I'll update this thread with my numbers once I've done it.
Why don't you just try to see how low it will go? I don't think undervolting will kill your chip. Heck I have my current 9850 running at 0.85v at 860MHz when in idle mode.
EDIT: Doesn't look like I'll be getting one. Gonna stick with this chip for about another year.
Why don't you just try to see how low it will go? I don't think undervolting will kill your chip. Heck I have my current 9850 running at 0.85v at 860MHz when in idle mode.
EDIT: Doesn't look like I'll be getting one. Gonna stick with this chip for about another year.
it wont kill it at all. most people who go for AMD probably dont think about undervolting. on the other hand every core2 chip i've had has given me 600-800 mhz with a .075-.1 volt reduction.
Ya I know undervolting doesn't damage anything (I've found the absolute limit on many lappy procs) I think will just go see how low I can take it, I'll let you guys know.
Grab PhenomMSRTweaker, make sure you turn off CoolnQuiet in the BIOS. Fire up 2 instances of Orthos custom test 512KB size, lock the 2nd instance to cores 3 and 4, run both, and start decreasing your voltage for whatever Ghz you want. Make sure you're watching the voltage in CPU-z. PhenomMSRTweaker references voltage to whatever you have in BIOS. So I had my voltage at 1.475 and increased the PhenomMSRTweaker voltage from 1.325 (default in the program) to 1.475 and then noticed my cpu-voltage had jumped up to 1.62v. YIKES. Luckily I hadn't loaded it.
First I used speedfan to set what fan duty cycle I wanted for quiet operation. IE, @25%, I want it to be able to take a full load and dissipate all the heat without having to spin any faster.
The CPU locked up around the lower 0.9x volts when I was running it at 4x200mhz. So I figured what the heck, if I have to be at 0.9v, might as well see what I can get out of it. So I set to a little over 1v to be 100% safe and then just started playing with the multiplier, increasing it 0.5x at a time. Locked up at 12 on the way up, didn't lock up at 11.5 on the way up so I set to 11 to be safe.
Usually the Orthos will fail without the computer hard-resetting. Makes finding max/min freq and voltages very fast.
This is all basic OC'ing stuff which I'm sure you already know. I guess I just got wordy and felt like typing it. Kudos if you read this far, haha.
Silent pc found 1.175 to be min. stable on their Athlon II 250, and 1.1875 on their Phenom II 550. These should be fairly representative of 940 (and 45nm AMD in general) results. http://www.silentpcreview.com/article949-page3.html
If you guys use PhenomMSRTweaker I guarantee you can get lower than that, down to 0.95 probably.
Yea-- It's completely liberal, unlike Intel Speedstep. It only allows you to set 2 P-states-- which only makes sense, there's little point if having 5 steps to full speed since if you need to escalate one P-state on a Quad core you're going to need to escalate all the way to full speed.
I found 1.21v to be the lowest I could run 3ghz at but the failure mode (stress test shut down gracefully) leads me to believe I missed something.
At 1.2v I could only run my X3 720 at 2.7ghz, so I would recommend you underclock down to 2.7/8/9 to get it stable.
Cool. I've just been experimenting with this today on my 955BE. Currently I've been running all day at 1.250v and throwing load and it and it's working just fine. Might try to drop it down to 1.225v and see if it'll run there.
Mainly I was doing this to drop CPU temps as i'm running the stock heatsink fan. Right now after using the machine for 2 hours or so I'm running 38C. If I push load it goes up into the 46-48C range, so reducing core by .1v has caused a 2C (idle) and about a 5C load drop in temps for me, which I'm real happy with. Keeps the factory fan on the CPU from hitting it's "second gear" noise level which was really bugging me.
Mainly I was doing this to drop CPU temps as i'm running the stock heatsink fan. Right now after using the machine for 2 hours or so I'm running 38C. If I push load it goes up into the 46-48C range, so reducing core by .1v has caused a 2C (idle) and about a 5C load drop in temps for me, which I'm real happy with. Keeps the factory fan on the CPU from hitting it's "second gear" noise level which was really bugging me.
phaxmohdem
Golden Member
I just got my shiny new PII 940 today, and upon installing it in my cramped mid tower case, discovered that even at stock speeds, it would hit the high 70's and throttle down to 800MHz, Not cool. So I undervolted it to try and get the heat under control a bit.
I successfully got mine down to 1.250 (BIOS) 1.280 (CPUZ) seemingly stable. I haven't gamed on it at all yet, but I ran about half an hour of 100% usage 3D rendering on it to test.
I'm going to shuffle my video cards around tonight and stick the 8800GTX in the bottom slot of my motherboard so that it is not butted up against the cpu heatsink,,, which probably isn't helping matters seeing as that card hits the 90C mark fairly easily when in use.
I successfully got mine down to 1.250 (BIOS) 1.280 (CPUZ) seemingly stable. I haven't gamed on it at all yet, but I ran about half an hour of 100% usage 3D rendering on it to test.
I'm going to shuffle my video cards around tonight and stick the 8800GTX in the bottom slot of my motherboard so that it is not butted up against the cpu heatsink,,, which probably isn't helping matters seeing as that card hits the 90C mark fairly easily when in use.
How mcuh did your undervolt help the temps? Try taking it lower, I generally find absolute min stable and then increase it .0125v. I've never had a prob with this system. Those temps (70s) seem really high, I'm running the 940 in a crappy Rosewill uATX case with a 9600GSO and not seeing anything over 50deg.
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