Undervolt Videocard? Has anyone been able to? If so how?

Serenity · Post by **Serenity** » Sat Oct 06, 2007 6:57 pm

There must be a way!

My videocard is already cooled mostly silently.....

The issue is it still makes lots of heat...even idle in windows... (6800GT, AGP).

The big issue is it's heating up the entire case.... Emanating forth it's heat making the entire case much warmer. The cpu produces almost 0 heat... It's 2.4ghz Athlon64 (s754) downclocked to 800mhz & undervolted from 1.5 to 0.8 (as low as it can possibly go).

The nvidia overclocking utility allows one to downclock the card. It's 350mhz stock (core) & 1000mhz (memory). I have it downclocked from 350/1000 to 100/400. So it is running much slower.... but this does not affect the high-temperature it maintains while idle....it needs to be undervolted. Problem is, I haven't a clue how!

Flandry · Post by **Flandry** » Sat Oct 06, 2007 7:39 pm

Sadly, nVidia doesn't really care.

I don't believe there's any way to do this, short of fiddling with the PCB.

Phido · Post by **Phido** » Sun Oct 07, 2007 4:01 am

Check bios customisers

I belive the overvolters pioneered much here. Pencil tricks or little modification and you should be able to undervolt.

Flandry · Post by **Flandry** » Sun Oct 07, 2007 4:35 am

Phido wrote:Check bios customisers

I belive the overvolters pioneered much here. Pencil tricks or little modification and you should be able to undervolt.

It may be possible with a BIOS mod for older cards. The 8x00 series (so far, anyway) appears to support only two very similar voltages, and i've not heard of anyone who has successfully set it to use the lower of the two -- in spite of inquiring about this in several places last month with hopes of greatly reducing power at idle. I don't have a card yet to try it.

The pencil trick generally pulls the Voltage up by reducing the resistance across a voltage regulator's leads (where a resistor is already in place). There maybe be an alternative position to modify that decreases the Voltage, but there's no easy way to increase the resistance across the leads that those overvolters are using, which is what would be necessary to undervolt.

MoJo · Post by **MoJo** » Sun Oct 07, 2007 12:06 pm

You can drop the voltage by replacing a resistor, but it won't be software changeable so might not be stable at full speed. Sadly there is no software mod.

You should be able to get your clocks lower though. Try ATI Tool. I can get an 8800 Ultra down to 200/200 before it starts to become unstable.

Serenity · Post by **Serenity** » Sun Oct 07, 2007 3:01 pm

I have it heavily downclocked already... (from 350/1000 to 100/400) [core/mem].

However, that only affects temperatures when at full load-----when idle the temperatures are near identical whether at stock speeds or heavily downclocked. The same goes for my cpu.... If I downclock it, but do not undervolt it, the idle temperature does not change almost at all... The downclocking is only useful in that it enables you to undervolt while maintaining stability.

I'm not giving up. There has to be a way to do this without ripping the cards circuitry apart!

More people should join the fray in trying to find some reliable way to do this----it would be a huge boon to the SPCR crowd if we could have a way to undervolt video cards just like we can with CPU's!

MoJo · Post by **MoJo** » Mon Oct 08, 2007 1:58 pm

You should be able to get your mem down to 200 at least. I found that reducing core speed only made a >1C difference at idle, but reducing mem speed made an 8C difference.

Sadly that really is all you can do. Well, you could install a variable resistor on your card to adjust voltage. I have seen that done before. I'm not sure if the mod only controls core voltage though, as there was no mention of memory voltage. Dropping memory voltage would help a lot more I think, or better still nVidia could move to GDDR4.

Thomas · Post by **Thomas** » Tue Oct 09, 2007 2:04 am

I've serached a lot for undervolting options for VGA cards, and have found nothing usefull. The above posts sums up very well, what I've found.

I'm doing reasonably well with soldering, but not good enough for soldering the very small SMD components. So I havent tried swapping the resistor with a potentiometer. And then again, will it run full speed, if undervolted?

I'm in doubt what you want to achieve? Is it only a matter of case temp, or is it also noise and lower wattage?

Personally, I look at it this way: If it's stable and quiet, I'm satisfied. Well, maybe except for HDD temps, where I prefer to be lower than 40

Anyway, if it's about case temps, and you dont want to swap the card, then I believe you'll have to work with the case and airflow.

Recently, I swapped my 9800Pro VF-900 cooler to an Accelero S2. That made better airflow possible, so now my S2 is passive, and my P180 upper chamber is cooled only by 2 12 cm Nexus' @ 5 volt. And my CPU and NB temp dropped a couple of degrees.

My 9800 Pro is 30,5 watt idle, where the 6800GT is 23,4 (both stock speeds and according to XBitLabs).

The 9800Pro is 47,3 full load, the 6800GT is 55,4.

6800GT: http://www.xbitlabs.com/articles/video/ ... wer_3.html
9800Pro: http://www.xbitlabs.com/articles/video/ ... ons_8.html

The Accelero S1 should be better than my S2, and the S1 should fit 6800GT AGP - but DO check the height restriction drawing from AC, if you consider this solution

AC S1: http://www.arctic-cooling.com/vga2.php?idx=138

But depending on your current case, VGA coller, etc., there might be other ways...

Vicotnik · Post by **Vicotnik** » Tue Oct 09, 2007 7:10 am

On my 7950GT it was not to hard to lower the Vcore. While it required a hard mod, no soldering was required. If the 6800GT uses something like the Intersil ISL6568 for controlling the voltage maybe you could do something similar to your card.

More about the mod here
- viewtopic.php?t=36145

Right now I'm running the card @ 550/1500, 1.1v (default was 580/1500, 1.25v). I think the memory voltage shuld be tweakable as well but I haven't checked.

Thomas · Post by **Thomas** » Tue Oct 09, 2007 10:20 am

Very nice Vicotnik, thanks. I'll check out if my 9800Pro uses that Intersil, or someone similar

EDIT:

This link indicates my card uses a Intersil ISL6522CB (have to check on my card though, since it's another variant).

But apparently, it's much complicated to change the voltage output from the 6522CB