Undervolting my mobile barton

[Connoisseur]

Hey, I felt like making my system cool and quiet so I set my mobile barton (35w 2200+) to 5x200. The only problem is my motherboard (biostar M7NCD Pro) will only set the core voltage as low as 1.30V. Is there any way to circumvent this limitation (any kinda mod trick)? I'm almost completely sure that at this low frequency that the voltage can be reduced much more to get it even cooler... any success stories?

 

[L00PY]

In theory you could set the default processor voltage down to as low as 1.1V through a pin mod, so if your mobo will correctly recognize voltages that low, it should work. You'll have to do some work to figure it out though.

Voltages are specified through the VID[4:0] pins. Grab any of the tech docs off AMD's site and search through the PDF for the table of "VID[4:0] Code to Voltage Defintion" table. That'll give you the right codes to play with. Just like with the multiplier mods, you'll probably have to cut some bridges and then the right pins to the ground. Checkout what the Interactive Pin-Mod guide does for the higher voltages.

 

[3chordcharlie]

Out of interest; at 1ghz and 1.3 volts, that thing should be using about 15 watts... how much cooler do you want it?

What are the actual temps at the settings you have?

 

[jswjimmy]

my xp1800 runs fine with 1.1volt at 1530mhz. with how good the bartons oc i would think that it could do it to.
my computer would run at 28C under load with my volcano12 on low

 

[NewBlackDak]

Mine does the default 2GHz at 1.35. It makes almost no heat, and even the quietest HSFs will cool it like that. I see no reason why you should have to run at 1GHz.

 

[Connoisseur]

Allright this is the thing. I'm using an ALX-800 with AS5 and a Thermaltake Smartfan II running at 2600rpm. For whatever reason my temps won't read any lower than 37C idle and that's right after standby. Neither the cpu or case temp drops below this value regardless of how freezing cold my room temp is (I have an AC and at some points I have had my room temp in the 50's F). This is with the side panel both open and closed. What in god's name is happening here? charlie mentioned that my CPU at 1ghz and 1.3vcore only dissipates 15W. If this is the case, I should be able to cool this thing with the fan running at the minimal 1500 rpm and have lower temps. When I have the cpu at max OC (2.4ghz @1.7vcore) the temps go up to 47C idle and 54C load with the case completely closed. Can this be a temp reading issue? I'm completely sure I have the HS mounted on properly.

To clarify, i'm pretty sure I have enough airflow as I have 2 intake, 2 output, 1 side fan, and 2 psu fans pulling air out. WHY won't my temps go any lower???

 

[Concillian]

The ALX doesn't work well at very low fan speeds. It does pretty comparable to the copper coolers at nominal fan speeds, but it chokes at low speeds.

http://www.silentpcreview.com/modules.php?op=modload&name=Sections&file=index&req=viewarticle&artid=136&page=1

 

[3chordcharlie]

Originally posted by: Connoisseur
Allright this is the thing. I'm using an ALX-800 with AS5 and a Thermaltake Smartfan II running at 2600rpm. For whatever reason my temps won't read any lower than 37C idle and that's right after standby. Neither the cpu or case temp drops below this value regardless of how freezing cold my room temp is (I have an AC and at some points I have had my room temp in the 50's F). This is with the side panel both open and closed. What in god's name is happening here? charlie mentioned that my CPU at 1ghz and 1.3vcore only dissipates 15W. If this is the case, I should be able to cool this thing with the fan running at the minimal 1500 rpm and have lower temps. When I have the cpu at max OC (2.4ghz @1.7vcore) the temps go up to 47C idle and 54C load with the case completely closed. Can this be a temp reading issue? I'm completely sure I have the HS mounted on properly.

To clarify, i'm pretty sure I have enough airflow as I have 2 intake, 2 output, 1 side fan, and 2 psu fans pulling air out. WHY won't my temps go any lower???

BTW 15W is a guess, but it's only 35W@ default voltage and clock speed; it might be as much as 20W. You're clock speed is a little over half of default, and your voltage is down .15 (voltage 'squares' in power consumption equations though, so it's quite a lot).

I think this could definitely be a sensor issue though. Very few CPUs ever seeing operating temps in the 30s, and even most cases rarely get below 35-37C. Sensors might not be well calibrated to read these temps. I think a lot of watercooling and other cooling tests don't rely on sensor readings, for this very reason; particularly since it's most important that the sensor be accurate at or near 'dangerous' temperatures (for shutdown purposes). Manufacturers likely put little effort into calibrating sensors for temps in the 30s.

Also, your system temp is read from a sensor that may be near some other heat-generating component.

 

[NewBlackDak]

The CPU is not the only thing making heat in a case, and it looks like the thing making the LEAST heat in yours. Memory, HDDs, video cards, and motherboards all make heat. If they're all hot, and you have crap air-flow in your case it doesn't matter how good your CPU cooling is.