I've done a bit of undervolting with several CPUs and discovered that one can save quite a bit of energy with it, especially if you're involved in things like folding@home. Although the procedure is quite simple, finding out the minimum voltage values for your CPU takes a bit of time testing etc. It would be nice to have a collection of data that people can use as a reference point. Therefore I'd like to ask everyone who has undervolted his CPU to submit his results.

Here's a tutorial. It's a bit outdated but still useful. There's also a lot of info to be found on this forum as well.

Programs for undervolting (and -clocking):

RMClock
CrystalCPUID
or for notebooks Notebook Hardware Control

Programs for stress testing (there are many others):

Prime95
Orthos


WARNING: Although CPUs of same type and stepping usual share the same undervolting options, there can always be individual discrepancies. The results shown below are indications.


We're looking for minimum voltage at minimum clock speed and minimum voltage at stock speed (with a stable system of course). Here's what we've got so far:

Athlon XP 2500+ - Barton (1.83GHz)

Stock: 1.87 GHz (11*170) @ 1.375 V (stock 1.60v)


AMD XP 2500+ - Mobile Barton stock - 1.45V

Minimum: 1.5 GHz @ 1.200 V
Stock: 1.83 GHz @ 1.3600 V


AMD Sempron 64 3000+ (754) stock - 1.4V

Minimum: 0.8 GHz @ 1.100 V (lowest possible, E6 stepping bug)
Stock: 1.8 GHz @ 1.150 V
OC: 2,3 GHz @ 1.400 V


AMD Athlon 64 3000+ - Clawhammer (754) stock - 1.5V

Minimum: 0.8 GHz @ 0.825 V
Stock: 2 GHz @ 1,375 V


AMD Athlon 64 3200+ - Newcastle (754) stock - 1.5V

Minimum:
Stock: 2.2 GHz @ 1.300 V


Turion ML-30 - Lancaster (754) stock - 1.35V

Minimum: 0.8 GHz @ 0.800 V
Stock: 1.6 GHz @ 0.925 V


AMD Athlon 64 3000+ - Winchester (939) stock - 1.4V

Stock: 1.8 GHz @ 1.104-1120 V


AMD Athlon 64 3200+ - Venice (939) stock - 1.35V

Minimum: 1.0 GHz @ 1.100 V (-> Vcore lock)
Stock: 2.0 GHz @ 1.125 V

Minimum: 1.0 GHz @ 1.100 V (-> Vcore lock)
Stock: 2.0 GHz @ 1.125 V
OC'ed: 2.25 GHz @ 1.275 V
OC'ed: 2.5 GHz @ 1.425 V


AMD Athlon 64 3500+ - Venice (939) stock - 1.35V

Minimum: 1.0 GHz @ 0.800 V
Stock: 2.2 GHz @ 1.175 V
OC'ed: 2.7 GHz @ 1.325 V


AMD Athlon X2 4600+ - Manchester (939) stock - 1.35V

Minimum: 1.0 GHz @ 1.100 V (Note: lowest possible VID)
Stock: 2.4 GHz @ 1.225 V


AMD Opteron 165 - Denmark (939) stock - 1.35V

Minimum: 1.1 GHz @ 0.825 V
Stock: 1.8 GHz @ 1.000 V
OC'ed: 2.5 GHz @ 1.250 V


AMD Opteron 170 - Denmark (939) stock - 1.35V

Stock: 2.0 GHz @ 1.100 V


AMD Opteron 185 - Denmark (939) stock - 1.35V

Minimum: 0.8 GHz @ 0.800 V
Stock: 2.6 GHz @ 1.200 V


AMD Athlon 64 3000+ - Winchester (AM2) stock - 1.4V

Minimum: 1.0 GHz @ 1,1 V
Stock: 1.8 GHz @ 1,175 V


AMD Athlon 64 3000+ - Orleans (AM2, Revision F2) stock - 1.4V

Minimum: 1.0 GHz @ 0.825 V
Stock: 1.8 GHz @ 1.100 V


AMD Sempron 64 3200+ - Manila (AM2) stock - 1.35V

Minimum: 0.8 GHz @ 0.800 V
Stock: 1.8 GHz @ 1.000 V

Minimum: 0.8 GHz @ 0.800 V
Stock: 1.8 GHz @ 0.900 V (not thoroughly tested)


AMD Sempron 64 3400+ (AM2) stock - 1.35V

Minimum: 0.8 GHz @ 0.800 V
Stock: 1.8 GHz @ 1.000 V


AMD Sempron LE-1100 - Sparta (AM2) stock - 1.35V

Minimum: 0.8 GHz @ 0.800 V
Stock: 1.9 GHz @ 0.950 V (12 hrs Orthos)

Minimum: 0.8 GHz @ 0.800 V
Stock: 1.9 GHz @ 1.000 V


AMD Sempron LE-1250 - Sparta (AM2) stock - 1.35V

Minimum: 0.8 GHz @ 0.800 V
Stock: 2.2 GHz @ 0.975 V


AMD Athlon 64 3500+ - Orleans (AM2, Rev. F2) stock - 1.35V

Minimum: 1.0 GHz @ 0.900 V
Stock: 2.2 GHz @ 1.100 V


AMD Athlon 64 3500+ - Lima (AM2) stock - 1.35V

Minimum: 1.0 GHz @ 0.800 V
Stock: 2.2 GHz @ 1.025 V


AMD Athlon X2 3600+ - Windsor (AM2) stock - 1.25V?

Minimum: 1.0 GHz @ 0.900 V
Stock: 2.0 GHz @ 1.075 V


AMD Athlon X2 3600+ - Brisbane (AM2) stock - 1.35V

Minimum: 0.8 GHz @ 0.800 V
Stock: 1.9 GHz @ 1.000 V

Minimum: 1.0 GHz @ 0.825 V
Stock: 1.9 GHz @ 1.000 V


AMD Athlon X2 3800+ - Windsor (AM2) stock - 1.35V

Minimum: 0.8 GHz @ 0.900 V
Stock: 2.0 GHz @ 1.125 V
OC'ed (sort of): 2.3 GHz @ 1.275 V

Minimum: 1 GHz @ 0.800 V
1.6 GHz (Crystal CPUID): 1.6 GHz @ 0.900 V
Stock: 2.0 GHz @ 0.975 V


AMD Athlon X2 4000+ - Brisbane (AM2) stock - 1.35V

Minimum: 1.0 GHz @ 0.856 V
Stock: 2.1 GHz @ 1.031 V

Minimum: 1.0 GHz @ 0.864 V
Stock: 2.1 GHz @ 1.056 V


AMD Athlon X2 4200+ - Windsor (AM2) stock - 1.25V

Minimum: 1.0 GHz @ 0.800 V
Stock: 2.2 GHz @ 1,125 V


AMD Athlon X2 4400+ - Brisbane (AM2, Rev. G2) stock - 1.3V

Minimum: 1.0 GHz @ 0.830 V
Stock: 2.3 GHz @ 1.010 V
OC'ed: 2.66 GHz @ 1.100 V
OC'ed: 3.00GHz @ 1.230 V

Stock: 2.3 GHz @ 0.960 V


AMD Athlon X2 4800+ - Brisbane (AM2) stock - 1.225V?

Minimum: 1.0 GHz @ 0.800 V
Stock: 2.5 GHz @ 1.200 V


AMD Athlon 64 X2 5400+ - Brisbane (AM2, Rev. G2) - stock 1.325V
Minimum Voltages
Minimum: 1.0 GHz @ 0.775 V
Stock: 2.8 GHz @ 1.225 V


AMD X2 BE-2350 (AM2) stock - 1.25V

Warning: system wasn't stable, need more input from others

Minimum: 1.0 GHz @ 0.825 V
Stock: 2.1 GHz @ 1.000 V


AMD X2 4450e (AM2) stock - 1.25V

Minimum: 1.0 GHz @ 0.850 V
Stock: 2.3 GHz @ 1.100 V


Intel Pentium III-S (Tualatin) 1.26 GHz

1.36 GHz (142 MHz FSB) @ 1.45 V (stock voltage not adjustable on my mobo, processor multi is locked)


Intel Pentium M Dothan 1.0 GHz

Minimum: 0.6 GHz @ 0.700 V (lowest possible)
Stock: 1.0 GHz @ 0.748 V


Intel Pentium M Banias 1.3 GHz

Minimum: 0.6 GHz @ 0.796 V (original 0.956v)
Stock: 1.3 GHz @ 1.180 V (original 1.340v)


Intel Pentium M Banias 1.4 GHz

Minimum: 0.6 GHz @ 0.700 V
Stock: 1.4 GHz @ 1.100 V (original 1.484v)


Intel Pentium M Dothan 1.5 GHz

Minimum: 0,6 GHz @ 0.700 V (original 0.988v)
Stock: 1,5 GHz @ 0.972 V (stable at 0.940, I add two VIDs for daily use, original 1.340v)


Intel Pentium M 735 Dothan 1.7 GHz

Minimum: 0.6 GHz @ 0.700 V (lowest possible, original 0.988v?)
Stock: 1.7 GHz @ 1.004 V


Intel Pentium M 745 Dothan 1.8 GHz

Minimum: 0.6 GHz @ 0.716 V
Midway: 1.4 GHz @ 0.908


Intel Pentium M 760 Dothan 2.0 GHz

Minimum: 0.800 GHz @ 0.700 V - Note: lowest possible VID
Stock: 2.0 GHz @ 1.068 V (stock 1.356v)


Intel C2D Mobile T2500 - Yonah (479) stock - ?

Minimum: 1.0 GHz @ 0.950 V
Stock: 2.0 GHz @ 1.100 V


Intel C2D Mobile T5600 - Merom (479) stock - 1.15V

Minimum (SpeedStep, 1GHz): 1.0 GHz @ 0.850 V (lowest possible)
Stock: 1.83 GHz @ 0.870 V

Stock: 1.86 GHz @ 0.950 V - lowest possible VID


Intel C2D Mobile T7400 - Merom (479) stock -

Minimum: 1.0 GHz @ 0.975 V (it's locked, won't go lower)
Stock: 2.16 GHz @ 1.04 V


Intel C2D E2140 - M0 (775) stock - 1.325V

Stock: 1.6 GHz @ 0.925 V
OC'ed: 2.8 GHz @ 1.325 V
OC'ed: 3.0 GHz @ 1.400 V
All value come from bios setting.

Minimum: 1.2 GHz @ 0.825 V
Stock: 1.6 GHz @ 0.887 V
OC'ed: 2.66 GHz @ 1.187 V


Intel C2D E2160 - M0 (775) stock - 1.325V

Minimum: 1.4GHz @ 0.850 V


Intel C2D E4300 - B2 (775) stock - 1.35V

Stock: 1.8 GHz @ 1.000 V (motherboard limited)
OC'ed: 2.4 GHz @ 1.2125 V
OC'ed: 2.7 GHz @ 1.325 V


Intel C2D E6600 - Conroe (775) stock - ?V

Minimum: 1.6 GHz @ 1.136 V (Note: lowest possible VID)
Stock: 2.4 GHz @ 1.136 V
OC'ed: 2.76 GHz @ 1.136V (notes: same voltage as with speedstep at this frequency!!)
OC'ed: 3.1 GHz @ 1.340V (notes: overclocked to maximum stock voltage)

Minimum: Haven't tried
Stock: 2.4 GHz @ 1.000 V
OC'ed: 3.0 GHz @ 1.175 V


Intel C2D E6750 - Conroe (775) stock - 1.35V

Minimum: 2.0 GHz @ 1.187 V
Stock: 2.66 GHz @ 1.187 V
OC'ed: 2.8 GHz @ 1.212 V
OC'ed: 3.2 GHz @ 1.325 V


Intel Core 2 Quad Q6600 - Kentsfield (Rev B3, Stepping 7) stock - ?

Minimum:
Stock: 2.4 GHz @ 1.31250 V (Temps 70.0/51.0; 1.6 GHz speedstep)
Stock Minimum: 2.4 GHz @ 1.16875 V (Temps 62.8/48; 1.6 GHz speedstep)


Intel Core 2 Quad Q6600 - Kentsfield (Rev G0, Stepping 7) stock - 1.35V

Minimum:
Stock: 2.4 GHz @ 1.0375 V

Minimum: 2.0 GHz (333x6) @ 1.000 V


Intel Core 2 Quad Q9450 - Yorkfield (Rev C1) stock - 1.225V?

Minimum:
Stock: 2.66 GHz @ 0.99375 V



If you have any suggestions to improve this thread, please tell me.

AMD Opteron 165 - Denmark (939) stock - 1.35V

low: 1.1GHz @ 0.825V
Stock: 1.8GHz @ 1.000V
OC'ed: 2.5GHz @ 1.250V

My sugesstion, as I listed, is to add successful OVERCLOCK & UNDERVOLT settings. As you can see, I would be my power expense would be 25% higher with the OC above, but my productivity would rise by an even larger amount - 38%. Therefore, while my power bill would be higher with the OC, my contribution to folding@home would outweigh the expense.

AMD Athlon 64 3500+ - Venice (939) stock - 1.35V
Minimum: 1.0GHz @ 0.800V
Stock: 2.2GHz @ 1.175V
OC'ed: 2.7GHz @ 1.325V


Intel C2D E4300 - B2 (775) stock - 1.35V
Stock: 1.8GHz @ 1.000V (motherboard limited)
OC'ed: 2.4GHz @ 1.2125V
OC'ed: 2.7GHz @ 1.325V

Thanks for posting, miahallen and dragmor!



All data is interesting, so I'll be sure to add them.


ps I added stock voltages to some of the other CPUs

AMD X2 3800+ Windsor (AM2) stock 1.35V
Minimum: 0.8GHz @ 0.900V
Stock: 2GHz @ 1.125V
OC'ed (sort of): 2.3GHz @1.275V

And for my curiosity I've tested it like in picture below, but it was unstable at FID/VID transitions with RMClock.

Good shout Palindroman

Perhaps drop it into the folding forum too.....


Pete

Opteron 170 CCBBE 0617 FMPW
Currently at 2.2ghz, 1.15v
Was at 2.0ghz, 1.1v

I have not tested the lowest I can undervolt given a low multiplier because the machine is constantly folding, and low clock speeds aren't my aim.

this is the same mentality I've been using. I'm trying to find a balance between WU frame time and power consumption. But I'm also limited because I want to run my chip fanless, so I'm almost at the thermal limit, I really want to stay with a 2-fan system.

Intel C2D Mobile (Merom) T7400

stock idle freq/volt: 1.0 GHz @ 0.975v
stock busy freq/volt: 2.16 GHz @ 1.21v

undervolt idle: 1.0 GHz @ 0.975v (it's locked, won't go lower)
undervolt busy: 2.16 GHz @ 1.04v

am not overclocking.

Thanks for the results, everyone!



Is 0.975 the stock voltage for the T7400? Or is that with Speedstep enabled?

I've got my Opteron 185 running at 0.8V at 800MHz in its idle mode, and 1.2V @ 2.6GHz under full load. (Stock is 1.35V at full load, 1.1V @ 1GHz in idle.) It's rock solid at both of these extremes, but the 800MHz setting only works if you also reduce the HT speed to 800MHz (default is 1GHz) in the BIOS.

At stock voltage (1.35V) I've overclocked it to just over 3.0GHz. Much faster than that it gets unstable; I haven't tried raising the voltage to push it further.

i have an e6300 at 1.1v overclocked to 2400mhz [400x6].

Nice, I like that

AMD Opteron 165 - (S939) stock - 1.35V
2.5Ghz @ 1.350V
1.8Ghz @ 1.050V
1.1Ghz @ 0.900v

AMD Athlon X2 3600+ - Brisbane (AM2) stock - 1.35V
2.7Ghz @ 1.275V
2.0Ghz @ 1.025V
1.3Ghz @ 0.850V

AMD Athlon X2 3600+ - Brisbane (AM2) stock - 1.35V
2.4Ghz @ 1.275V
1.9Ghz @ 1.000V
1.3Ghz @ 0.900V
1.0Ghz @ 0.800V

just curious, is it able to be cooled passively at these settings? (ie no CPU fan)

Well, speedstep has been abled since the first boot, so I'm sure
that's what the 0.975 thing is. I'm sure it could go lower than that
at 1.0 GHz, but it's locked in the sense that the CPU ignores requests
for a VID less than that.

Sure, but probably not with the stock cooler. any good Aftermarket cooler should do it no problem as long a your case had a little bit of airflow.

All Core2 processors are designed to run at 1.05V while idling (ie, with SpeedStep enabled), and almost all of them will operate at load at close to this voltage if kept cool. Some will operate at load at lower voltages, but not much lower...

Interesting results I've seen:

Pentium M Dothan - 1.3v?
1.5ghz @ 0.908v
1ghz @ 0.716v
600mhz @ 0.7v

Turion ML-30 - 1.35v
1.6ghz @ 0.925v
800mhz @ 0.8v

Athlon64 x2 4000+ Windsor AM2 - 1.35v
2.7ghz @ 1.35v
2.0ghz @ 1.1v
Haven't tried lower than 1.35ghz/1.1v because the fan turns off already, don't see a point.

Intel E4300 with Gigabyte P965-DS3 m/b Stock voltage - 1.325V
Stock clocking 1.8GHz
Won't post under 0.925V
Won't boot into XP under 0.96875V but random reboots at this voltage.
Stable for > 10 hours Orthos testing at 0.98725V

AMD Athlon X2 3800+ 35W - Windsor AM2 stock - 1.075V
1.3G @ 0.85V
2.3G @ 1.1V

No trial of extremely undervolt yet.

AMD Athlon 64 3500+ - Orleans (AM2)

Minimum: 1.0GHz @ .925V
Stock: 2.2GHz @ 1.150V

I've updated the results, but please post only the minimum voltages at which your system is stable. It's the extremes we want to know here.


What is the stock voltage of this one, do you know? There Orleans-core Athlons with different power envelopes, I believe.

I'm using ASUS BIOS to run a Brisbane 4800+ at 1.1V. (Hasn't been stable at lower voltages).

Maybe you should try your hand at undervolting through RMClock (depending on your OS of course)?

I guess I'll repost mine, though, I haven't tried for low multi+min voltage

Opteron 170 Denmark (939) - Stock 1.35V
Min Stock(2.0ghz) 1.1v
2.2ghz 1.15v(so far)

Merom T5600 Stock 1.15V
min stock (1.86 GHz) 0.95 V - lowest possible VID

Thanks, I've added your results.

If I may ask, how come the Meroms don't go below a 0.950v (T5600) and 0.975 (T7400) respectively. According to this site it should be able to vary between 0.75~1.3V.

e6300@ 1.125v 2.4ghz, 400x6, 1600mhz FSB......... stable as stable can be.

C2D E6300 @ 2.8GHz (400 x 7) 1.1625v

48 hours Orthos stable.