2D vs 3D clocks

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Jakalwarrior

2[H]4U
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Aug 6, 2005
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A post about power conservation over on xtremesystems got me thinkin. A lot of cards have seperate 2d and 3d clocks right? why are the 2d clock so high? Try underclocking it some time. You can go waaaaay down before any difference whatsoever is noticeable. Why arent they set that way on stock to reduce power consumption? better yet, why not have 2 phases of 2d clocks like CNQ, one at some miniscule amount like 150 core, the other at around 300 core (all depending on the card) for when you are watching video or a web page covered in flash.

I cut my 2d clocks in half and still notice no slowdowns. Not even in video play back (though my screen is smallish so no 1080p stuff).
 
Does it really cut power consumption that much though? How much does the memory take versus the GPU itself? I've often wondered why video cards don't have a speed step equivalent - I figured maybe it was because of the memory. My comp draws 200+ watts from the wall just idling, and probably half of that is the video card (my similarly equipped integrated graphics server draws 80), so it would be nice if there was a way to cut that power draw.
 
The ram is clockable easily with software too, they could just include than in any speed step type stuff.
You have a kill a watt? If so you could find out real fast for yourself. Just use ATI tool to clock each part way down seperately and see how much juice each is using.
Since some of the new gpus idle at 40*C + though they must be drawing a good bit of juice just sitting there. My ram on the other hand is usually cool to the touch when idling.
 
I usually use ATI Tool with all my video cards. When the program starts, I have it underclock the video card. I use the 3D detection feature to raise the clocks to my overclocked settings when I go gaming. When I exit the game, the clocks are once again reduced. On the 7900 GS is have now, I clock at 250 core 350 memory in Windows, and then overclock to 600 core 850 memory in games. It helps keep the cooling fans spinning slow when I want them to.

Nvidia cards have built-in 2D/3D mode clocks, but I'm not a huge fan of using them as they don't reduce the memory clock at all; only the core clock speed changes. I haven't had a modern ATI card in a while, so I'm not sure how their 2D/3D mode stuff works.
 
Jakalwarrior said:
The ram is clockable easily with software too, they could just include than in any speed step type stuff.
You have a kill a watt? If so you could find out real fast for yourself. Just use ATI tool to clock each part way down seperately and see how much juice each is using.
Since some of the new gpus idle at 40*C + though they must be drawing a good bit of juice just sitting there. My ram on the other hand is usually cool to the touch when idling.
Click to expand...

I do have a kill-a-watt. Just tried it with my 8800GTS - even with core, shader, and mem clocks as low as Riva can set them my system draws the same power. Strange.

Actually, it doesn't seem to be working correctly, because even though I changed my normal settings (performance 3d, which is the profile that runs all the time) it didn't change my 3dMark score at all. So it either isn't working, or the card is internally clocking back up even though I told it not to. GPU-z does show the lower clocks though.
 
Well I have an ATI card and run Atitool to start at windows startup for all users and set all clocks to 250/250 with 3d detection enabled so as soon as a 3d app starts, the card runs at 540/530. Works like a charm and I even have different fan profiles for the different clock speeds.
 
If you arent also lowering your voltages during 2D then it's not going to save all that much power.
 
It does use less current, though. Like when you overclock, more energy is being used and more energy released in the form of heat, even when you're at a constant voltage.
 
skadebo said:
It does use less current, though. Like when you overclock, more energy is being used and more energy released in the form of heat, even when you're at a constant voltage.
Click to expand...

Agreed.

However, you can usually also get away with less volts at a lower clock speed, thus increasing your efficiency. This is what makes the new HD3800's use a lot less power in 2D mode. For instance, the 3850 has a lower 2D voltage than the 3870 (same 300Mhz gpu clock in 2D) and as a result, the 3850 uses less power at idle (even the 512mb model). At identical 3D clock speeds, the 3870 would still use more power than the 3850. Why? Cause the 3870's 3D voltage is higher. If you can lower the voltage in your circumstance I would do it.

Learned all this modding my 3850's bios, btw.
 
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