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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  • Mathos - Wednesday, October 15, 2008 - link

    No idea why they used quad core, other than the fact that a quad would spend more time in low power mode and have lower CPU usage than a dual. That and there are no AMD dual cores out yet that use HT 3.0, although the x2 6500 should be. Most of the AMD based boards are adversely effected by using an older X2 instead of something that uses HT3.0.

    Anyone not seeing the point of a 780g/790gx board, or an nForce 8200/8300 board for an HTPC is not thinking. The point is to not need a discrete card. Many HTPC's use low profile cases, which make finding an adequate video card difficult. Not to mention with the 780g/790gx you can later install a $50 discrete 3650 or 3450 and run it in Xfire with the IGP for better gaming performance. Same goes for the lower end 8000 and 9000 cards on the nforce chipset.

    As far as the PSU goes it leaves room for possibly adding in a discrete card later. Also remember that most PSU's are most effecient at around 50% load which happens on some of the AMD systems under heavy load. Not to mention if you want to have a silent PSU you need to keep the load low so the fan isn't humming constantly, which would happen on a lower rated PSU.
    Reply
  • tonyintoronto - Wednesday, October 15, 2008 - link

    The issue is the 780G just doesn't work well enough to be used in htpc.. tons of issues with hdcp and different monitors/tv's, still can't decode mpeg2 stream without crashing the display driver, issues with open GL, was a great idea but bad drivers/hardware have done it for me.. now, the 9300 and 9400 looking nice :) Reply
  • Mathos - Tuesday, October 14, 2008 - link

    Hmmmmm Actually the power numbers aren't too bad when you take it into context. Q9300 is a 45nm chip, and 9950 is 65nm. Q9300 is 95w TDP rated, but runs much lower actual TDP. While the 9950 is rated 125w TDP. I'd be interested in seeing this test redone once Deneb variants come out. Considering the lesser performance of the Phenom compared to the Penryn, it actually speaks well of both the AMD based chipsets, and shows that the 790GX does a lot to make up for the processor.

    I'd say AMD/ATI are doing a good job on the Chipset front now.
    Reply
  • Calin - Tuesday, October 14, 2008 - link

    Also, considering we're talking about a $174 versus a $260 processor. I wonder what the results were if the comparation would have been against the quad core Q6600 (at a somewhat similar price of $189). Reply
  • 3DoubleD - Tuesday, October 14, 2008 - link

    "However, they are offering 8-channel LPCM support on the HD 4xxx series of video cards. Of course that option comes with an additional cost and potential problems such as incompatibility with AVR receivers such as those from Yamaha"

    Can you elaborate on these problems? I was planning on building an HTPC system and was considering this exact combination. Are these temporary (driver update solvable) problems?

    This second question is only distantly related to this article. When using the HDMI with LPCM audio, will sound from sources other than Blu-ray discs (such as games or movies with DD5.1 or DTS) be playable on your stereo? Part of me wants to say yes it will for DTS and DD5.1, but I'm skeptical about video games for some reason. I guess I don't fully understand the extent of the sound card capabilities on these IGP/discrete graphics solutions.

    Great article, I'm looking forward to your HTPC graphics card review.
    Reply
  • AmdInside - Tuesday, October 14, 2008 - link

    I own the Asus M3N-H/HDMI (Geforce 8300) and except for the fact that it doesn't have an eSATA port, I have no complaints (well, maybe the placement of the 24-pin power connector).

    http://www.asus.com/products.aspx?modelmenu=1&...">http://www.asus.com/products.aspx?model...mp;l1=3&...

    I recently purchased the Intel G45 Mini-ITX motherboard to build a second HTPC and although it has worked ok for the most part, BD and HD-DVD playback just doesn't seem as smooth as the Geforce 8300. It is not choppy. It just feels like the framerate is lower. I can't explain why. The same HDTV was used with both systems and they were both set to 1080p/60. Both systems are running Windows Vista. If you are building a new HTPC, I would not recommend Windows XP btw with these platforms. Anyways, I appreciated the article. For me, I was trying to build a somewhat portable HTPC with the Intel mini-ITX motherboard but given the problems I am having with BD and HD-DVD playback, I think I am going to leave it as a Windows Media Center DVR box and use the Geforce 8300 as my main HTPC. For what it's worth, I tested with both WinDVD and Arcsoft TMT.
    Reply
  • gipper - Tuesday, October 14, 2008 - link

    It sounds to me like you're really recommending that at this time the way to go is to get a cheap Intel chipset motherboard with the cheapest, lowest power 45nm Core2 Duo, and an ATI 4550.

    But what Intel chipset would give that rock solid platform at the lowest price?
    Reply
  • tayhimself - Tuesday, October 14, 2008 - link

    Neither AMD nor Nvidia can make a decent chipset. Intel seems to have as many misses as they have hits so they're usually a good bet. Boo hiss to poor QC! Reply
  • Nil Einne - Friday, January 30, 2009 - link

    As with others, I have to say this is a piss poor review. I looked at the Part 1 and came across a resonably decent review. Was expecting the same thing here. But what do I come across? You onmly test two quad cores. What idiot buys a quad core for their HTPC? Unless you're transcoding there's absolutely no reason and given the price of HDs nowadays and the fact that some broadcasters are using AVC for their HD content anyway there's only a few people who are going to bother. Even if you are occasionally transcoding, it's questionable of you really need a quad core or it might be better to just stick with a dual. At the very lest you could have tested quad cores and dual cores like you did with the previous review. But you didn't and so have a fairly useless review for 99% of the population. Why did you even bother with gaming anyway? Seriously, how many people game with quad core IGP systems particularly the kind of games you were testing. And how many of those check out Anandtech reviews? Maybe 5 people in the whole world... You may use a quad core IGP for a high load server or a non-3D workstation but not gaming.

    As it stands, based on your previous review (part 1, i.e. the one with the G35) and your comparison between the G35 and G45 I'm guessing that the 8200 is probably still better when paired with a decent CPU for most HTPC purposes but only barely. Sadly it's just a guess for the reasons I outlined above
    Reply
  • Nil Einne - Friday, January 30, 2009 - link

    When I said part 1 I meant the "IGP Power Consumption - 780G, GF8200, and G35", got slightly confused. One of the strangest things about this review of course is the 8200 performed so poorly whereas in that review, it was better then the 780G. Has the 780G improved a lot? Is it just the Gigabute 780G was a POS? Who knows, one would have thought the reviewer would have at least co=mmented on if not investigated this but apparently not Reply

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