As we all know, when running ATI GPUs in dual screen, it idles much higher than in single screen (500/1250 vs 150/250).

I was wondering if we can use something like Afterburner to underclock the GPU to the minimum needed for playing video. I'm not sure what that would be though. Playing video without DXVA on single screen leaves the clocks at 150/250 but with DXVA it goes to 500/1250 anyway, so maybe that is the minimum needed. Then the question becomes whether it's more energy efficient to play stuff without DXVA (leaving it to the CPU) with the GPU clocks at 150/250, or to reduce the load on the CPU by letting the GPU handle the decoding at 500/1250?

ATI Tray Tools is the ultimate software for ATI/AMD cards. You'll have to create an underclock profile to prevent the frequencies from ramping up at UVD levels when a hardware accelerated video is playing and ditch the useless Catalyst Control Center.
My HD 4870 can play 1080p content without a hiccup at idle (160/225 MHz modded BIOS) in dual screen configuration.

No doubt ATI Tray Tools is great but it does seem to have some problems.

For instance, I set Deinterlace to Vector Adaptive and Pulldown detection On in CCC. In ATI Tray Tools however, it shows Deinterlace set to Auto-Detect and if I change it, it seems to do something (screen flashes) but when I check again it's gone back to Auto-Detect. Then I open CCC to check it, and I get an error about "MMdriver application has stopped working" (which I never got before running ATI-TT) which I close, and CCC shows Deinterlace is still on Vector Adaptive, but I can't be sure this is true as ATI-TT says something different.

There's a lot of other Video Options in CCC that ATI-TT doesn't show, which doesn't really matter to me as I disable them all anyway, but it would be nice to be able to check that they're disabled in ATI-TT.

Under Advanced Tweaks, it has ticks next to "Disable support for Adaptive AA" and "Disable support for High Quality AF" which seems wrong as well.

I can't really see where to make an underclock profile either, as on the Overclocking screen it won't let me go lower than my current clocks (450/1250). How would you stop it ramping up when playing video, but still let it go to full clocks when playing a game anyway?

I can see ATI-TT has a lot more features than Afterburner, but if I'm going to have to manually switch profiles when I want to game, I can do that with Afterburner which seems a lot simpler (well, I already know my way around it anyway). I just need to find out whether Afterburner can underclock.

Good to know that you can play everything at 160/225 with your 4870. Makes you wonder what the point of UVD is!

To add to my last post, my PC just crashed whilst ATI-TT was running, which it's never done before.

The screen just went black with stripy lines on it and I had to do a hard reset!

Running CCC AND ATT at the same time is a recipe for disaster.
Just kill the CCC process from the Task Manager and make sure that it doesn't load at startup and give it another try.
You don't have to manually switch profiles, in Hardware-->Auto Overclocking tick Enable auto 2D/3D overclocking with your 2D/3D custom profiles (you have to create them first).

OK, I'll try that.

Assuming it doesn't crash anymore, are you saying that you set the 2D profile to 160/225 and the 3D profile to full clocks (920/1375 for me) and it stays in 2D mode when playing hardware-accelerated video?

I also still don't know how to create a profile with lower clocks than I'm currently running at (450/1250).

Yes, in most of the cases. It works well with MPC-HC or XBMC, but with some players like Arcsoft's still jumps at full throttle, because I left unchanged the default UVD frequencies (750/900) in the modded BIOS and I don't want to flash my card again just for that.

Maybe it's the CCC's Overdrive fault, but if your card idles at 150/250 MHz I believe it can be done, it's just a matter of trial and error.
Good luck.

I wonder why some apps ignore ATI-TT and jump to UVD frequencies. I can't mod them in my BIOS anyway, as this isn't possible with the HD6950 apparently.



Maybe if I go to single-screen, where it idles at 150/250, I can set this in ATI-TT and it will honour it when I switch to dual-screen.

The best way would be to use RBE to export and edit your BIOS with the desired clock speeds and then flash it.

HD 6900 Series have dual BIOS so it's really fool proof.

Except I don't think the HD6900 series allow for the clock speeds to be altered in the BIOS.

I think I've found the solution to that problem: in ATT go to Tools & Options-->General Options-->Advanced and untick the Use overclocking limits option (at 50% by default).
Good luck and let us know how it went.

Thanks, that works. Unfortunately, I can't use ATT at the moment as it causes my PC to lock up some hours later. I haven't even tried to use any of it's features, other than to set the fan to 50% (as I've done in Afterburner), so I don't know why it's making my PC freeze.

What videocard are we talking about? You could use Radeon BIOS Editor (RBE) to alter the clocks.

If you look up a bit you'll see we're talking about the HD 6950, which doesn't allow for BIOS clock speed editing with RBE.

Catalyst 11.10 is out and it supports 5 screens...I wonder if the additional monitor support means even higher base clock rates or if they've tuned this a bit? I haven't tried it, yet. Please be my guinea pig

I still get 450/1300 with dual monitors.

I just found this on Anandtech:

Mmm... interesting. I also have the problem that ever since I went dual-monitor on my 5770, I can't enable Overclock or else I have weird refresh issues in 2D mode (just browsing the web, or simply idling on the desktop). That is even if the 2nd monitor is turned off (no power) as I don't use it all the time.

So not only did I had to give up the power saving, I also had to give up overclock... Is that fixed at least on cards from the 6000 series?

Yeah - I was disappointed when I read that part of the review. I think the only "fix" for me would be to just add a 2nd lower power card, like the HD6450 @ $30 (or whatever the 7xxx version is), and use that to drive my 2nd monitor's 2D apps.

I liked the part about the 3w "long idle" on the new ati card. I'm hoping to use the intel IGP for everything 2d and the ATI card purely for gaming. A gaming card you can basically turn off is something I have always wanted.

Me, too. Whether or not this is an available profile in the new generation desktop cards is yet to be seen.

It's because the memory clock change has to happen during vsync to avoid visual glitches. With multiple monitors, vsync isn't synchronized so you can't change clocks without glitches. AMD chose to disable clock changes, which is a shame.

FYI, HT4U is showing multi-monitor idle power in their reviews (shown here in Googlish).