We regularly look at power consumption when talking about card performance, and for this review we want to look at two different aspects of power consumption. Since these cards all have potential for home theater systems given their HDCP compatibility, we want to look at not only power consumption during game performance, but also during BD video playback.

3D Acceleration Power Consumption

It's important to be aware of how much power your card draws when gaming so undue stress isn't put on your computer's power supply. Also, high wattage power supplies have bigger fans to keep them cool; that means a card with a lower power draw might be more desirable in a system that is built for as quiet operation as possible. To test the power load of these cards during 3D acceleration, we recorded the total wattage of the system with each of the cards installed while the system was idle for reference (i.e. no programs running), and then we recorded the total wattage of the system while running a few of the demos from 3DMark06. The 3DMark06 demos put stress on the GPU and we can then compare this to the idle wattage to get a general idea of how power hungry a card is.

Idle Power

Load Power

We can see that as you would expect, higher performance cards like the Sapphire Radeon X1950 XTX as well as the EVGA and BFG GeForce 7950 GX2 saw some of the biggest power draws. The reference NVIDIA 8800 GTX required a bigger power supply than the one we used for the other cards, so we put in a more powerful one with the necessary two PCIe connectors for that particular configuration. This will make these power numbers less consistent with the others, but we can still get an idea of how power-hungry these new cards from NVIDIA are. These cards are going to require higher watt power supplies to run, and so might not be the best choice for a quiet system. We noticed that the Albatron 7900 GS had a lower power draw than the others in its class, and the Gigabyte 7600 GS was the least power-hungry of all of these cards (as well as the least effective in video decoding).

Blu-Ray Playback Power Consumption

We also want to look at power consumption while playing back a BD movie with these cards. Because 3D acceleration takes more processing power than decoding video, we will expect to see a lower power draw in these tests, but as with CPU utilization, we will probably be seeing higher power draws with future Blu-Ray and HD-DVD content which will make use of higher bitrate encoding.

We took power reading in the same way as with CPU utilization: by playing back about a minute of video from our Blu-Ray movie "Click." We are also interested in seeing the kinds of power loads these cards have when hardware acceleration is disabled in order to see the contrast between power loads. Because cards of the same family (i.e. 7900 GS, 7950 GT, etc.) saw very similar power consumption without hardware acceleration enabled, we only recorded power in this state for one of each card family. These are the results of our tests.

Bluray Playback Power Consumption - No Hardware Acceleration

Bluray Playback Power Consumption - With Hardware Acceleration

Again we see that not surprisingly, the higher performance cards see greater power draws than lesser performing ones, but we don't see a big difference here between most of the cards. In many cases, higher clocked cards of the same type see a little higher power draws than their competitors, but in some cases (like with the Leadtek WinFast PX7900 GS TDH Extreme) we see lower power draws. This tells us that there will be variation in power draw between cards of the same type depending on what types of modifications the different vendors make to their cards. Again keep in mind that we used a different power supply for the NVIDIA GeForce 8800 GTX, so it's not really an apples-to-apples comparison.

In the future, we could see power consumption go down with acceleration enabled. As graphics hardware is better suited to processing video than a CPU, efficiency should go up when using hardware acceleration. At this point, there isn't much difference, but this could change when we move away from MPEG-2 and into higher bitrate content.

CPU Utilization Heat/Noise
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  • rnemeth - Friday, December 1, 2006 - link

    I personally think this article was extremely on point with the direction of media components in general. I think there will be many people out there, like me, who are planning on the convergence of the Media Center PC & Gaming PC. Vista (Ultimate) will bring Media Center to the masses and why shouldn't you be able to play your favorite DX10 "Game for Windows" on your big HDTV as well?

    This article is ahead of its time. HDPC/DRM/HDMI/DVI/BR/HD-DVD/HDTV is all in the early stages. In the future, you will be able to buy or rent your high-def movie by downloading it to your PC with DRM finally figured out. This review shows us that it is not all there yet, but gives us an idea who is doing what, and what we need to look for.

    You mentioned in the beginning of the article that you were looking for feedback to see how interested your audience is on this subject... count me as 1.
  • thejez - Sunday, November 26, 2006 - link

    HDCP is a joke... look at how hard it is to understand and get this stuff running... not to mention you have upgrade all your hardware?? lol and who watches movies on their PC anyway?? do you people really sit huddled over your keyboard watching movies?? Why not invest in some better equipment for the family room and watch movies they way they were intended....

    but the difficulty in setting all this up makes it even more important that hdcp has already been cracked... i wouldnt let the movie industry tell you your hardware isnt good enough to buy their content... just buy what you want and "work" around the issue later... the cracks are only getting better.... we'll see HD-DVD Shrink soon enough...
  • KalTorak - Monday, November 20, 2006 - link

    Careful - it's not safe to assume that higher bitrate content is more computationally difficult to decode than lower bitrate content. [In fact, I suspect they're weakly correlated the other way - lower bitrate is harder.]
  • DerekWilson - Monday, November 20, 2006 - link

    ahh ... very interesting ...

    it would make sense to me to say that both are true.

    In the case where low bitrate means more aggressive high quality encoding, i absolutely see your point. But low bitrate can also mean lower quality (less information) at the same level of encoding -- in these cases lower bitrate will be easier to decode.

    Thanks for pointing this out.
  • Badkarma - Monday, November 20, 2006 - link

    Hi Derek,

    Can you comment on HD audio formats like Dolby TrueHD and DTS-HD for the HTPC? I know Bluray has yet to use these formats but how about HD-DVD on the HTPC. From what I understand, you could get these formats outputted via analog output on your soundcard, but I'm interested in HDMI. I know some of the HDMI video cards you reviewed have SPDIF passthrough via HDMI, however SPDIF cannot carry Dolby Digital +, TrueHD, or DTS-HD, it will only output DTS or DD. I'm holding back on a HDCP video card because HD audio is an important part of HD movies.

  • Ajax9000 - Sunday, November 19, 2006 - link

    p.13 "Both the 8800 GTX and GTS are fully HDCP compatible, and HDCP is enabled through both DVI ports" p.22 "Some of the cards, like the HDMI Gigabyte 7600 GS and ASUS EN7600 GT, were only able to play our Blu-ray movies over HDMI and not through the DVI port. Conversely, we found that with our MSI NX7600 GT Diamond Plus, the Blu-ray content wouldn't play through the HDMI connection but it would through the DVI port."

    OK, so which cards (other than the 8800s) could do HDCP over both ports?


    p.19 "The end result is that an NVIDIA card with more pipelines that is better at 3D performance will not necessarily be better at video decoding."

    In other words overclocking (say) a 7600 is likely to give as good or better HD video results than using (say) a 7950GX2?


    p.20 "In the future, we could see power consumption go down with acceleration enabled. As graphics hardware is better suited to processing video than a CPU, efficiency should go up when using hardware acceleration."

    The results for the 9750GTs already seem to show this 147W average non-accelerated >> 142 for EVGA & PNY (although Gigabyte > 148W).

  • chucky2 - Friday, November 17, 2006 - link

    ...can we get it added to these results just for comparison?

    Also, you don't happen to know when that'd be, would you? :)

  • BigLan - Friday, November 17, 2006 - link

    I noticed that in the cpu utilisation tests you said it was around 51% for no acceleration - was this because the player software is single threaded and so only used one core?

    Also, is click encoded in h264, or mpeg2 like the initial bluray discs?
  • DigitalFreak - Friday, November 17, 2006 - link

    Now that the Xbox 360 HD-DVD drive is available and is proven to work with a PC, any chance on doing another round-up "real soon now" using HD-DVD? I'd really love to see the numbers for VC1 and H.264 decoding.

    Still amazed that the lowly X1600 card spanked all Nvidia cards but the G80 boards in CPU utilization.

    Good job guys.
  • DigitalFreak - Friday, November 17, 2006 - link

    BTW, the new releases from Fox on Blu-Ray use the H.264 codec. Behind Enemy Lines, Fantastic 4, etc. I think Behind... is already out.

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