The New Face of PureVideo HD

The processing requirements of the highest quality HD-DVD and Blu-ray content are non-trivial. Current midrange CPUs struggle to keep up without assistance and older hardware simply cannot perform the task adequately. AMD and NVIDIA have been stepping in with GPU assisted video decode acceleration. With G84, NVIDIA takes this to another level moving well beyond simply accelerating bits and pieces of the process.

The new PureVideo hardware, VP2, is capable of offloading the entire decode process for HD-DVD and Blu-ray movies. With NVIDIA saying that 100% of the H.264 video decode process can be offloaded at up to 40 Mbits/sec on mainstream hardware, the average user will now be able to enjoy HD content on their PC (when prices on HD-DVD and Blu-ray drives fall, of course). There will still be some CPU involvement in the process, as the player will still need to run, AACS does have some overhead, and the CPU is responsible for I/O management.

This is quite a large change, even from the previous version of PureVideo. One of the most processing intensive tasks is decoding the entropy encoded bitstream. Entropy encoding is a method of coding that creates variable length symbols where the size of the symbol is inversely proportional to the probability of encountering it. In other words, patterns that occur often will be represented by short symbols when encoded while less probable patterns will get larger symbols. NVIDIA's BSP (bitstream processor) handles this.

Just adding the decoding of CABAC and CAVLC bitstreams (the two types of entropy encoding supported by H.264) would have helped quite a bit, but G84 also accelerates the inverse transform step. After the bitstream is processed, the data must go through an inverse transform to recover the video stream which then must have motion compensation and deblocking performed on it. This is a bit of an over simplification, but 100% of the process is 100% no matter how we slice it. Here's a look at the breakdown and how CPU involvement has changed between VP1 and VP2.

We have a copy of WinDVD that supports the new hardware acceleration and we are planning a follow up article to investigate real world impact of this change. As we mentioned, in spite of the fact that all video decoding is accelerated on the GPU, other tasks like I/O must be handled by the CPU. We are also interested in finding videos of more than 40 Mbit/sec to try and push the capabilities of the hardware and see what happens. We are interested in discovering the cheapest, slowest processor that can effectively play back full bandwidth HD content when paired with G84 hardware.

It is important to emphasize the fact that HDCP is supported over dual-link DVI, allowing 8600 and 8500 hardware to play HDCP protected content at its full resolution on any monitor capable of displaying 1920x1080. Pairing one of these cards with a Dell 30" monitor might not make sense for gamers, but for those who need maximal 2D desktop space and video playback, the 8600 GT or GTS would be a terrific option.

While it would be nice to have this hardware in NVIDIA's higher end offerings, this technology arguably makes more sense in mainstream parts. High end, expensive graphics cards are usually paired with high end expensive CPUs and lots of RAM. The decode assistance that these higher end cards offer is more than enough to enable a high end CPU to handle the hardest hitting HD videos. With mainstream graphics hardware providing a huge amount of decode assistance, the lower end CPUs that people pair with this hardware will benefit greatly.

Under the Hood of G84 The Cards and The Test


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  • shabby - Tuesday, April 17, 2007 - link

    3dmark vista edition of course! Reply
  • munky - Tuesday, April 17, 2007 - link

    Why did you not include the x1950xt in the test lineup? It can also be had for about $200 now, like the 7950gt. You didn't want to make the 8600 series look worse than they already do, or what? Reply
  • DerekWilson - Tuesday, April 17, 2007 - link

    Wow, sorry for the ommission -- I was trying to include specific comparison points -- 3 from AMD and 3 from NVIDIA, but this one just slipped through the cracks. Sorry. It will be included in my performance update. Reply
  • Elwe - Tuesday, April 17, 2007 - link

    Now, now guys. True that these cards are not going to be what many of you want (there are some good reasons to stay with what you have considering the performance differential of several of the last generation cards). And it is clear that these cards will not touch the 8800 cards (from what I can tell, the only these these do better are are 100% Pure HD on the card, which I guess is because these might be paired with not-so-great cpus.

    But for some of us, they might work. I recently bought a Dell 390 workstation. I packed it with fast drives, QX6700 cpu, and 4gb ram. There were very few BTO graphics choices, and most centered around the Pro market (this is a "workstation" after all). These is a new machine, and quite powerful! I want to work and play on this box. Because of the relatively week power supply (rated at 375 watts or something like that) and because I need both available non-graphics PCIe slots (if you put it an 8800 GTS, even if you changed the power supply, this type of dual slot card will cover one of those slots), I have been waiting for something reasonably powerful to come along (again, I am not going to just work on this box; I would like to play UT2k7, too:). Since I run Linux, I was trying to stick with the Nvidia line (my experience is that they have better drivers for this platform, but perhaps ATI has stepped up in the last half year or so). I could have gone with the 79xx line (single slot), but I wanted to see what the new generation would bring. Depending on what you need/want, I think either a slightly-used 7950GT OC or a 8600 GTS would work just fine for me. It does not seem unreasonable to me that in some things the older higher end card is faster than the newer mid range card, and vice versa. But I did not see any benchmark where the 79xx line whooped the 8600 GTS thoroughly (like what happend with several benchmarks comparing the 8800 and 8600).

    I would say that the only immediate problem I might have with using the 8600 GTS is for gaming at high resolutions. I have a Dell 2407, and Anandtech's benchmarks make it clear I should not be gaming at that high a resolution. Bummer. The 7950 GT OC might very well be the better option here.

    In an ideal world, I really would like the power of an 8800 (and, fortunately, I can pay for it). But I really need the PCIe slot more, and changing out the power supply would add even more cost. I could have gotten another Dell model (like the XPS 710 or the Precision 490)--and I am thinking about just that. But I got the 390 for what I considered good reasons (a damned sight cheaper than the 490, and I have no need of another cpu socket when I can have 4 cores in one socket), and the XPS 710 did not have BTO storage options that I wanted (not sure why they could not design that thing to have more than two internal drives--the thing is big enough; maybe most games do not need it, as that is what the machine was designed for). I bet I am not the only one.
  • GhandiInstinct - Tuesday, April 17, 2007 - link

    Masses would include AGP cards...

    I see no AGP DX10 cards...
  • aka1nas - Tuesday, April 17, 2007 - link

    The "masses" don't build their own computers, and thus have long since stopped purchasing machines with AGP slots. Reply
  • GhandiInstinct - Tuesday, April 17, 2007 - link

    The "masses" also don't go hunting for DX10 cards to add FPS to their hardcore Dell and Gateway gaming rigs.

    Be honest with yourself, the people going for these cards are custom riggers.

    AGP DX10 please, theres hundreds of thousands with Pentium 3.4 Northwoods that know their processors will run BioShock well, but they need DX10 without paying for a new motherboard, DDR2, and everything else, including Vista!!!
  • JarredWalton - Tuesday, April 17, 2007 - link

    Actually, I don't think anyone "knows" whether or not any current system will run BioShock well or not. Let's wait for the game to appear at least. We're still at least four months away (assuming they hit the current release date).

    While I can understand people complaining about the lack of AGP cards, let's be honest: why should either company invest a lot of money in an old platform? It takes time to make the AGP cards and more time to make sure the drivers all work right. At some point, the old tech has to be left behind. The cost to transition from an AGP setup to a PCIe setup is often under $100, so if the AGP cards had a $50 price premium you'd only save yourself $50 and still be stuck with the older platform.

    I figure AMD/ATI and NVIDIA basically ignored the complaints with X1900/7900 class hardware (the best was several notches below what was available on PCIe), and at this point I think they're done. I'd even go so far as to say we're probably now at the point where an AGP platform would start to be a bottleneck with current hardware - maybe not midrange stuff, but certainly the high-end offerings.

    Let's put it another way: why can't I get something faster than a single core 2.4GHz 1MB cache Athlon 64 3700+ for socket 754? Why can't I get Pentium D or Core 2 Duo for socket 478? Why do we need new motherboards for Core 2 Duo when socket 775 is used sing 915/925? Intel and AMD have forced transitions on users for years, and after a long run it's tough to say that AGP hasn't fulfilled its purpose. Such is the life of PC hardware.
  • GhandiInstinct - Tuesday, April 17, 2007 - link

    Good points, I agree with them all.

    Basically, I feel that my 3.2 northwood, 2GB ram is worth salvaging for BioShock and Hellgate, obviously not Crysis, but it's convenient that it will be released in 08.

    I figure I can hold out 8 more months, save up during this time, and switch to quad and DDR3.

    I service hundreds of clients a week in tech support that have AGP setups, and I don't think Nvidia and ATi will abandon AGP with DX10, especially since there is speculation to believe they will be releasing this cards in the future:">

  • LoneWolf15 - Tuesday, April 17, 2007 - link

    While it would be nice to have this hardware in NVIDIA's higher end offerings, this technology arguably makes more sense in mainstream parts. High end, expensive graphics cards are usually paired with high end expensive CPUs and lots of RAM. The decode assistance that these higher end cards offer is more than enough to enable a high end CPU to handle the hardest hitting HD videos. With mainstream graphics hardware providing a huge amount of decode assistance, the lower end CPUs that people pair with this hardware will benefit greatly.

    IMO, this is absolute bollocks.

    If I'm paying for nVidia's high-end stuff, I expect high-end everything. And this is at least the second time nVidia has only improved video on their second-round or midrange parts (anybody remember NV40/45?).

    I game some, and I want good performance for that. But, I also have a 1920x1200 display, and I want the best video playback experience I can get on it. I also want the lower CPU-usage so I can playback video while my system is left to do other processor-intensive tasks in the background.

    Once again, nVidia has really disappointed me in this area. In comparison, ATI seems to be much better at making sure their full range of cards supports their best video technologies. This (along with nVidia's driver development) continues to make the G80 seem like a "rushed-out-the-door" product.

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