There are plenty of CPU overclocking threads recording top speeds achieved by individuals, giving a rough idea what one can expect out of these chips. How about recording the undervoltability of CPUs which we know is more relevant for the SPCR enthusiast. I suspect the AMD 90nm chips with it's competetive price/performance and low power consumption (plus based on forum postings) are most widely used for quiet/silent rigs so that will be the focus of this thread.

For the format, my initial suggestion are as follows, but of course this is open to changes/additions.

1. Socket : s939 or s754
2. Model : Sempron 3000+, A64 3500+, Turion ML44, etc.
3. Core/Revision : D0, E3, E6, etc (can be read by CPU-Z)
4. Speed: in ghz and ideally at stock speed for easy comparison
5. Vcore Setting=Vcore Reading: the undervolt at which your system runs stable. Setting is the value you set (in BIOS or CrystalCPUID or other software utility) and Reading is the value off your mb monitor, CPUZ, Speedfan, etc.

(additional info - if you have this)
6. CPU Temps : load/idle/ambient
7. Cooling : brief desc of your cooling
8. AC Draw : load/idle
9. System : brief desc of your components
10. Other comments

I'll start with some of my undervolting experiences

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s939 A64-3500+ Rev E3 (Venice) 2.2ghz stock ** 1.20v = 1.28v
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AC under Prime 77W @1.20v, 95W @1.40v
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ASUS NF6150, 512M RAM, 3.5" HDD - Prime 4+ hours, will do more testing

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s939 Opteron 164 Rev E4 (Venus) 1.8ghz stock ** 1.05v = 1.01v
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DFI NF4 MB - Prime 4+ hours, will do more testing

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s754 Sempron 3000+ RevE6 1.8ghz stock ** 1.20v = 1.17v
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AC under Prime 60W @1.40v, 52W @1.20v, idle 31W
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Asus P2-AE2 w/ 1G RAM, 2.5" HDD, DVD burner - Prime 18+ hours

s939 A64 3000+ Stepping D0 (Winchester) 1.8GHz stock ** 1.1V=1.08V

Not got accurate measurements for temps etc but passive cooling not possible at this clock and Vcore; possible at 1GHz @ 0.85Vcore.

Cooling: CM Hyper 48
AC draw: no idea, sorry
M/B: Asrock Combo-Z
all other components generic, ie DVD, seagate HD etc.

I have a question: can you cool the Opteron passively at that Vcore?

I also see you've got the Asus Pundit slimline barebone; congrats! How is it? Did it come with a slimline optical drive included?

I don't have much experience with passive cooling, but suspect it might be possible although not easy. My setup is with a fanned XP120, will try to post up some temps/wattage details in the next few weeks (sorry don't have access to this system till then)


My experiences with the Pundit here.

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s939 A64-3700+ Rev F7? (San Diego) 2.2ghz stock ** 1.125v = 1.14v
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AC under Prime95 @ stock 2.2ghz: (idles at 99 watts @ 1.1v)
1.10v = 116w = 41*C after 30+ min
1.125v = 118w
1.15v = 118w
1.20v = 124w
1.25v = 128w
1.30v = 131w
1.35v = 136w = 47*C after 15 min
1.40v = 141w
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ASUS A8N Premium, 445/1070mhz 7800GT, 2048M RAM, 4x160gb SATA HDD, S12-600 - Prime 24+ hours, stock OEM AMD HSF w/ fan at 1800rpm according to Speedfan

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s939 x2 3800+ Rev BH-E4 LDBHE 0537 XPMW (Manchester) 2.0ghz stock ** 1.175v - Dual Prime95 stable
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Asus A8N-vm CSM gf6150, 2x512M Ram, 3.5" hdd, odd, nx-4090 psu, Zalman 7000b-alcu
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Idle temp 38c @ 1200-1300 rpm (cannot tell for sure, since Speedfan doesn't give readings below 1400rpm. Max temp under dual prime95: 44c @ 1700rpm. Ambient temp guesstimate 18c.
Undervolting by CrystalCPUID, cannot give less then 1.175v due to overvolting motherboard. Setting in CCPUID @ 1.125v.

Edit: My computer had a random reboot yesterday, so I increased the voltage from 1.15v to 1.175v.

=======================================================
s939 A64-3000+ Rev DH8-D0 (Winchester) 1.8GHz stock ** 1.150v = ??v
---------------------------------------------------------------------------------------------------
AC and temps under Prime95 (1.8GHz, CPU fan @ 1050RPM, ambient 18.5°C)
70W, 31°C @ 1.400V
59W, 25°C @ 1.175V - - System's normal operating setting
59W, 24°C @ 1.150V - - Prime stable overnight (~10 hours)
---------------------------------------------------------------------------------------------------
AC under CPUburn (1.8GHz)
73W @ 1.400V
61W @ 1.175V
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Two level wooden platform | MSI RS480M2-IL | 2x256MB Corsair XMS DDR400
Arctic Cooling Freezer 64 | Seasonic SS-301HT | Seagate 7200.7 PATA 40GB
LG combodrive | Nexus 120mm fan

I used to run this system at 1.98GHz ** 1.250V. It ran stable that way for almost a year, but it is no longer stable at that setting

New system still under construction

s939 A64-3000+ Revision DH-E6 (Venice) 1.8GHz @ 1.136v cooled by XP120 + Papst 120mm

Prime95 83w 45oC @ 1.136v

Idle 63w 39oC @ 1.136

Mobo: biostar tforce6100-939
Graphics: onboard 6200
Sound: Creative audigy 2 zs
Network: netgear gigabyte PCI
Hard Disk: Raptor 150GB

S754 Sempron 3000+ (Rev. DH-E6 Venice)
Cooled by Zalman 7000AlCu (set at low end of Fan-Mate voltage range)

Stock 1.8GHz @ 1.075V (set in BIOS)
Prime95 44C

Underclocked 1.6GHZ @ 1.000V
Idle 32C
Prime95 40C

1. Socket : S939
2. Model : Opteron 146
3. Core/Revision : E4
4. Speed: 2 GHz (2 GHz stock, just showing undervolt result)
5. Vcore Setting=Vcore Reading: 1.025V + 0.02 V = 1.02 V

7. Cooling : Zalman CNPS7000A AlCu

9. System : DFI LanParty nF3 Ultra-D
10. Other comments : Great undervolting, yeah. But it's still a hot running chip, it wouldn't be cooled passively even in idle and outside case, this CPU have a lot in common with the hot running FX-57. Great overclocker though, 2.85 GHz at 1.39 V.

1. Socket : s939
2. Model : A64 3500+
3. Core/Revision : E3
4. Speed: 2.2ghz 512kb L2
5. Vcore Setting= 1.2v
2.2ghz = 1.1v (Requires 1.2v to boot)
2.0ghz = 1.1v
1.8ghz = 1.15v
1.6ghz = 1.025v
1.4ghz = 0.95v
1.2ghz = 0.95v
1.0ghz = 0.9v
0.8ghz = 0.8v

6. CPU Temps : 34c/23c/21c (Winter) 54c/46c/40c (Summer)
7. Cooling : Shuttle ICE (900RPM)
9. System : Shuttle SN95G5v3, 1gb Geil UltraX 2-2-2-5 2.8v, 9550, 250gb 7200.9, Liteon DVD Combo

10. There are a couple of oddities:
a) The chip requires 1.2v to hard boot, but is 24hr P95 and 24 StressCPU stable at the voltages listed above.
b) CrystalCPUID and RMClock refuse to set the voltage below 1.1v but the bios has no problems setting the value at 0.8v
c) If I leave it at 1.2v in the bios CnQ sets it to 1ghz with 0.925v at idle, which is fine for me.

Yeah, I have to admit, I bought my Winchester core about a year ago just because it was much lower power at stock than anything else out there. But now that I've tinkered around with it, I'm amazed at what it can do in terms of low-voltage operation. From the looks of it, Venice is even better.

Socket 939 A64 3200+ Rev DH8-D0 (Winchester) 2.0 GHz stock 1.4v / 1.1v

Lowest voltage at 2.0 GHz: 1.15v (20w DC draw load, est)

Lowest voltage at 1.0 GHz: 0.085v (5w DC draw load, est)

I've also been impressed by how easily the core overclocks. I have mine clocked at 240 MHz HTT with 5/4 memory divider, default voltage, so everything is stock except the processor frequency.

With the stock voltage, I run Cool 'n Quiet as well, and get the best of both worlds: 2.4 GHz at load, and 1.2 GHz at idle. Of course, now you can do this with CrystalCPUID, but back when I bought this, if you wanted Cool 'N Quiet voltage / frequency scaling, you had to have stock voltage.

Don't know why everyone is making such a fuss over Turions...seems almost every single 0.09 micron Athlon 64 can hit 1.2v at stock frequency.

Has anyone got any recommendations for micro-atx s939 undervolting motherboards (not GeForce 6150 based... the linux drivers seem somewhat lacking at the moment) ?

I'm looking at using a venice core but my search for a suitable matx mobo is proving difficult.

Any suggestions welcome!

Can we keep this thread on topic? Please ask your mobo questions in a separate thread.

I'm currently running my X2 3800+ undervolted/-clocked with the ability to instantly increase clockspeed and voltage if required with RMclock...

Currently @ 1,9GHz with 1,104 volts; even load temps remain below 45 degrees with this
If required @ 2,7GHz with 1,328 volts; dual-core load temps at 53 after 7 hours of prime.

Wow, check this out:

I undervolted my Winchester 3200+ to 1.0v, and tested the highest clock I could push it to. I managed to get it up to 1.5 GHz, booting from BIOS at those settings. Finished SuperPI 32M while running Prime Torture.

Best of all, I ran it PASSIVE with my Zalman 7000 AlCu, which was really nice, because even at 7v it was the loudest fan in my system. Temps leveled out at 42C. There were only one 120mm fan (7v Vantec Stealth) + 80mm PS fan in the system (Antec Sonata), virtually silent.



I estimate that the Winchester at 1.0v, 1.5 GHz uses about 11w DC full load:

Known full-load wattage (29w) * frequency scale * voltage^2 scale

29w * (1.5 GHz / 2.0 GHz) * (1.0v^2 / 1.4v^2) ~ 11w.

If I could passive cool with a puny Zalman 7000 AlCu at 1.5 GHz, it may be possible to cool an Athlon 64 clocked at or near stock with 1.1v, if you had a beefier heatsink. But you can't do it completely passive (ie, no airflow), not unless you drop it down to the 1 GHz range with 0.9v or so.

I run my XP-120/Winchester 3000+ at 1.1v with no heat sink fan. Stock frequency settings.

What sort of temps do you get under load with that setup?

s939 A64 3000+ Rev E3 (Venice) 2250MHz overclocked ** 1.2v

Prime95 stable.

Sorry, I can't supply results at stock speeds, but I remember that it wouldn't boot with less than 1.1v.

This particular chip is of the infamous CBBLE 0512 DPBW stepping/week. I have another running in a gaming rig thats happily does 2700MHz at stock voltage, so the underclocking results are not too surprising.