AMD's Cool'n'Quiet: Disable it

One interesting phenomenon that we encountered during testing on the AMD/NVIDIA platforms with the Phenom series of processors is the effect of Cool’n’Quiet (CnQ) on our BD playback results. We utilized a Phenom 9950BE in our test results today along with the 780G/GF8200/790GX chipsets. When playing back our H.264 title, The Simpsons Movie, with CnQ disabled we noticed an average CPU utilization of 6%~7% with platform power averaging anywhere from 132W to 140W depending on the chipset and motherboard. Video playback was smooth and stutter free on this title and many others regardless of the encoding format utilized.

One of the prime objectives for our HTPC systems is energy saving, especially during playback operation - the idea being that lower power use produces less heat and should therefore also result in a quieter system. The quickest way to reduce platform power on an AMD based system is to enable CnQ. After enabling CnQ in the BIOS and setting our Vista power management profile to balanced or power saver, we noticed our platform power requirements dropped to 99W~112W. This is a 25% or so improvement in power savings so we were naturally pleased with the results.

We fired up Power DVD 8 Ultra, popped The Simpsons Movie back in and decided to see how well the system operated. Our CPU utilization numbers increased to 16%~23%, but considering our processor and lack of background activities, this increase was perfectly acceptable. At least until we sat through this movie and others. We started to notice slight stutters, pauses, and even some judder at various times during the movie. At times, it was very pronounced but other times it was very subtle, but it was not so subtle that we did not notice.

The most frustrating part is that it never occurred in the same section of a title or at the same time. We would notice stuttering in the first 30 seconds of a title at times and other times it would not occur at all. In every case with CnQ enabled, we eventually noticed this behavior, regardless of chipset on the AMD platform. Turning off CnQ resulted in an immediate improvement in our viewing experience. We are investigating this problem (actually it has occurred in the past on the Athlons but not to this extent), but until then our suggestion is leave CnQ off and suffer the consequences of increased power usage. (Or at least, leave it off if you're putting together an HTPC.)

Hardware Blu-ray Decode Acceleration Hardware Accelerated Blu-ray Playback Comparison
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  • sergev - Monday, January 12, 2009 - link

    A fair comparison? Don't think so! A AMD processor with a 140 Watt TDP and a Intel processor with a 95 Watt TDP?? I wonder why the intel chipsets seem more power efficient? If you are testing the performance, ok seems fair, but power efficiency should be measured with two processors with the same TDP. I am convinced that if you did the same test with a AMD 4850E the AMD would beat the crap out the intel versions on power consumption. But yet again, that would not be fair. So keep in mind that this review is not to be taken al to seriously! Reply
  • axiomhk - Tuesday, October 28, 2008 - link

    Hi, what amazes me is that it seems no reviewers of the AMD IGP chipsets have caught the serious 2D issues referred to here:

    http://forums.amd.com/game/messageview.cfm?catid=2...">http://forums.amd.com/game/messageview....9&th...

    However, the only channel that we consumers / mere mortals have to put pressure on AMD is to send feedback to the Catalyst team. Nothing seems to get done and there is not even any acknowledgement that this issue exists across the HD3200/HD3300 IGPs no matter which manufacturer.

    The 3D performance is hyped up and that's all very well when the chipset has shown that it can deliver, but in fact many users will spend a lot of time on 2D activities which truly suck. This makes a lot of users regret their purchase.

    What the renowned sites such as anandtech and tomshardware can do is try to reproduce the issues, then use their direct contacts to try to see if this issue is being addressed and update the parent article accordingly. Is it possible? Many thanks. GM - Hong Kong.
    Reply
  • Zap - Wednesday, October 15, 2008 - link

    "The keyboard is not available after drive recognition until the Windows startup routine"

    Try a different keyboard, or a PS/2 keyboard. I had the same problem with two MSI 750a boards and some Razer USB keyboards. No keyboard until Windows. I had to fix a BIOS problem and had to borrow a keyboard - Logitech G15 USB keyboard worked fine.
    Reply
  • arjunp2085 - Wednesday, October 15, 2008 - link

    Is this not a bit ODD to Compare a $260 to a Lowly Under performing [B}$173 CPU... Geezs This is Grossly inaccurate

    Think about the BOOST to Post Processing and It differs a Whole Lot to the Post processing capability
    Reply
  • Strid - Wednesday, October 15, 2008 - link

    Yeah, it would have made more sense, IMO, to use lower end processors like AMD 4850E or Intel E5200/7200 which is what most people would use in a HTPC.

    But if you want to do encoding on your HTPC also, I can see the need for a quad core. But not for your average "movie box".
    Reply
  • Staples - Tuesday, October 14, 2008 - link

    Really, this thing came out like 6 months ago it seems and finally we get some video benchmarks on anandtech. I know it has been commented that it did not work right for months because the video drivers were terrible but I can not believe it really took that long. When I had to get a HTPC, I just bought an Athlon BE and a 780G board. Much cheaper and adequate. Which in hindsight the P45 may have performed better, an Intel CPU and a Core 2 CPU would have driven the price up quite a bit. Reply
  • Kreed - Tuesday, October 14, 2008 - link

    Gary, what are you hinting at with the following statement?

    "That leaves the Intel G45. If you are an Intel fan, this is your only real IGP choice... for the next few days at least."

    Are you suggesting that Intel might be releasing a new IGP over the
    Reply
  • Kreed - Tuesday, October 14, 2008 - link

    Oops, i didn't get to finish the comment. Here's the comment in full:

    Gary, what are you hinting at with the following statement?

    "That leaves the Intel G45. If you are an Intel fan, this is your only real IGP choice... for the next few days at least."

    Are you suggesting that Intel might be releasing a new IGP over the next few days?
    Reply
  • Strid - Wednesday, October 15, 2008 - link

    The NVIDIA MCP7A (GeForce 9300/9400 IGP) boards supposedly launches today. They're sockey 775 boards. I'm pretty sure AnandTech will have a review up soon.

    http://www.silentpcreview.com/forums/viewtopic.php...">http://www.silentpcreview.com/forums/viewtopic.php...
    Reply
  • steveyballme - Tuesday, October 14, 2008 - link

    Clearly Nvidia!


    http://fakesteveballmer.blogspot.com">http://fakesteveballmer.blogspot.com
    Reply

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