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 Post subject: Undervolting confusion and underclocking
PostPosted: Mon Feb 11, 2008 12:10 pm 
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Heylo. Browsed this section for a bit now and I cant seem to figure out a few things:

When you write about 'undervolting' in BIOS. Are you refering to graphics card BIOS or motherboard BIOS? Is there a difference and how do they play out?

And how about 'underclocking'? Is it possible on newer generations?
As I recall it was the only way to get old GPUs to work on lower voltage and get lower power consumption. Might seem like a dud to underclock but in my case (and many others) I only need the increased bandwidth and other features of new GPUs .. I do not need as much raw clockspeed.

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 Post subject: Re: Undervolting confusion and underclocking
PostPosted: Mon Feb 11, 2008 12:27 pm 
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Yomat wrote:
And how about 'underclocking'? Is it possible on newer generations?
As I recall it was the only way to get old GPUs to work on lower voltage and get lower power consumption.


Underclocking (and some limited undervolting) is controllable via software on most new GPUs.


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 Post subject: Re: Undervolting confusion and underclocking
PostPosted: Mon Feb 11, 2008 2:04 pm 
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Undervolting in video cards can be very challenging. It's hard to undervolt most cards in software at all. And only some can be undervolted(with some work) in bios. The only guaranteed way is through hardware mods. I've found most video cards are already clocked VERY close to their stability point, even undervolting .1v can require underclocking. My 7900 is stable at stock speeds, but a .1v undervolt causes instability unless I drop from 650 to 620.

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 Post subject: Re: Undervolting confusion and underclocking
PostPosted: Wed Feb 13, 2008 5:05 pm 
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aaa wrote:
Underclocking (and some limited undervolting) is controllable via software on most new GPUs.

That must be via GPU bios then.

merlin wrote:
Undervolting in video cards can be very challenging. It's hard to undervolt most cards in software at all. And only some can be undervolted(with some work) in bios. The only guaranteed way is through hardware mods. I've found most video cards are already clocked VERY close to their stability point, even undervolting .1v can require underclocking. My 7900 is stable at stock speeds, but a .1v undervolt causes instability unless I drop from 650 to 620.

Yes. Assumed as much. I probably opt for undervolting + underclocking. I rather buy a mid-end card. Seems like build quality is sometimes suffering on low-end cards. Then its only a matter how low you can go with undervolt+underclock. There must be some kind of limit.

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 Post subject:
PostPosted: Wed Feb 13, 2008 11:58 pm 
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my reference 8800gt is undervolted in bios to 1.0v, and is 1040mv instead of 1080mv when load. used nibitor and nvflash@usbdrive,bootable

with nibotor edit xtra voltage and clocks and save and then flash

maybe it will be possible with 9600GT, the new midend

at default clocks 1.05/1.00/0.95 resulted 185/176/172W with atitool in a hurry.

halflife2 demanded 40mhz lower for stability,

halflife2 clocks as follows

650/950 1.00
580/900 0.95

idle saves as much as ~ 5W

clock speed has no effect at all! in idle, 300mhz or 600mhz core, the system is the same ~110W, maybe i'm wrong, that's what i see. memory saves 4W when 1/2 clock.


Last edited by yuu on Thu Feb 14, 2008 2:10 pm, edited 2 times in total.

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 Post subject:
PostPosted: Thu Feb 14, 2008 6:13 am 
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yuu wrote:
my reference 8800gt is undervolted in bios to 1.0v, and is 1040mv instead of 1080mv when load. used nibitor and nvflash@usbdrive,bootable

with nibotor edit xtra voltage and clocks and save and then flash


And you left the default core/memory clocks as they were?
Any stability issues?

I'm tempted to do this. Wonder how many W I could save as I underclock when idle anyway, and only boost the clock rates when I need the hardware acceleration (use RivaTuner for this).


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 Post subject:
PostPosted: Fri Feb 15, 2008 12:07 pm 
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yuu wrote:
clock speed has no effect at all! in idle, 300mhz or 600mhz core, the system is the same ~110W, maybe i'm wrong, that's what i see. memory saves 4W when 1/2 clock.

Interesting. Do you have a temp sensor on your GPU? Would be interesting if that changes between 300mhz and 600 mhz.

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 Post subject:
PostPosted: Wed Feb 20, 2008 5:22 pm 
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Thanks, yuu. Seems like it makes no difference for temp either. Ah well.. indicates that its probably a safer bet to go for a lower end card. Unless, as already mentioned, you're into doing some real hw modification.

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 Post subject:
PostPosted: Thu Feb 21, 2008 10:40 am 
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I realize a 7800GT is pretty old nowadays, but it's all I've got. Below are my undervolt and underclock performance and temperature results on my 7800GT. I made the voltage changes by reflashing the GPU BIOS using NiBiTor.

Image

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 Post subject:
PostPosted: Thu Feb 21, 2008 4:33 pm 
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Anyone have experience underclocking a 8800GT with Coolbits? Does it work as well as ATiTool. I've had great success with my X800 XT PE and ATiTool.

-Ed

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