AMD Radeon HD 7970 Review: 28nm And Graphics Core Next, Together As One
by Ryan Smith on December 22, 2011 12:00 AM EST- Posted in
- GPUs
- AMD
- Radeon
- ATI
- Radeon HD 7000
Video & Movies: The Video Codec Engine, UVD3, & Steady Video 2.0
When Intel introduced the Sandy Bridge architecture one of their big additions was Quick Sync, their name for their hardware H.264 encoder. By combining a specialized fixed function encoder with some GPU-based processing Intel was able to create a small, highly efficient H.264 encoder that had quality that was as good as or better than AMD and NVIDIA’s GPU based encoders that at the same time was 2x to 4x faster and consumed a fraction of the power. Quick Sync made real-time H.264 encoding practical on even low-power devices, and made GPU encoding redundant at the time. AMD of course isn’t one to sit idle, and they have been hard at work at their own implementation of that technology: the Video Codec Engine (VCE).
The introduction of VCE brings up a very interesting point for discussing the organization of AMD. As both a CPU and a GPU company the line between the two divisions and their technologies often blurs, and Fusion has practically made this mandatory. When AMD wants to implement a feature, is it a GPU feature, a CPU feature, or perhaps it’s both? Intel implemented Quick Sync as a CPU company, but does that mean hardware H.264 encoders are a CPU feature? AMD says no. Hardware H.264 encoders are a GPU feature.
As such VCE is being added to the mix from the GPU side, meaning it shows up first here on the Southern Islands series. Fundamentally VCE is very similar to Quick Sync – it’s based on what you can accomplish with the addition of a fixed function encoder – but AMD takes the concept much further to take full advantage of what the compute side of GCN can do. In “Full Mode” VCE behaves exactly like Quick Sync, in which virtually every step of the H.264 encoding process is handled by fixed function hardware. Just like Quick Sync Full Mode is fast and energy efficient. But it doesn’t make significant use of the rest of the GPU.
Hybrid Mode is where AMD takes things a step further, by throwing the compute resources of the GPU back into the mix. In Hybrid Mode only Entropy Encode is handled by fixed function hardware (this being a highly serial process that was ill suited to a GPU) with all the other steps being handled by the flexible hardware of the GPU. The end goal of Hybrid Mode is that as these other steps are well suited to being done on a GPU, Hybrid Mode will be much faster than even the highly optimized fixed function hardware of Full Mode. Full Mode is already faster than real time – Hybrid Mode should be faster yet.
With VCE AMD is also targeting Quick Sync’s weaknesses regardless of the mode used. Quick Sync has limited tuning capabilities which impacts the quality of the resulting encode. AMD is going to offer more tuning capabilities to allow for a wider range of compression quality. We don’t expect that it will be up to the quality standards of X264 and other pure-software encoders that can generate archival quality encodes, but if AMD is right it should be closer to archival quality than Quick Sync was.
The catch right now is that VCE is so new that we can’t test it. The hardware is there and we’re told it works, but the software support for it is lacking as none of AMD’s partners have added support for it yet. On the positive side this means we’ll be able to test it in-depth once the software is ready as opposed to quickly testing it in time for this review, however the downside is that we cannot comment on the speed or quality at this time. Though with the 7970 not launching until next year, there’s time for software support to be worked out before the first Southern Islands card ever goes on sale.
Moving on, while encoding has been significantly overhauled decoding will remain largely the same. AMD doesn’t refer to the Universal Video Decoder on Tahiti as UVD3, but the specifications match UVD3 as we’ve seen on Cayman so we believe it to be the same decoder. The quality may have been slightly improved as AMD is telling us they’ve scored 200 on HQV 2.0 – the last time we scored them they were at 197 – but HQV is a partially subjective benchmark.
Finally, with Southern Islands AMD is introducing Steady Video 2.0, thesuccessor to Steady Video that was introduced with the Llano APU last year. Steady Video 2.0 adds support for interlaced and letter/pillar boxed content, along with a general increase in the effectiveness of the steadying effect. What makes this particularly interesting is that Steady Video implements a new GCN architecture instruction, Quad Sum of Absolute Differences (QSAD), which combines regular SAD operations with alignment operations into a single instruction. As a result AMD can now execute SADs at a much higher rate so long as they can be organized into QSADs, which is one of the principle reasons that AMD was able to improve Steady Video as it’s a SAD-heavy operation. QSAD extends to more than just Steady Video (AMD noted that it’s also good for other image analysis operations), but Steady Video is going to be the premiere use for it.
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chiddy - Thursday, December 22, 2011 - link
Ryan,Thanks for the great review. My only gripe - and I've been noticing this for a while - is the complete non-mention of drivers or driver releases for Linux/Unix and/or their problems.
For example, Catalyst drivers exhibit graphical corruption when using the latest version (Version 3) of Gnome Desktop Environment since its release before April. This is a major bug which required most users of AMD/ATI GPUs to either switch desktop environments, switch to Nvidia or Intel GPUs, or use the open source drivers which lack many features. A partial fix appeared in Catalyst 11.9 making Gnome3 usable but there are still elements of screen corruption on occassion. (Details in the "non-official" AMD run bugzilla http://ati.cchtml.com/show_bug.cgi?id=99 ).
AMD have numerous other issues with Linux Catalyst drivers including buggy openGL implementation, etc.
Essentially, as a hardware review, a quick once over with non-Microsoft OSs would help alot, especially for products which are marketed as supporting such platforms.
Regards,
kyuu - Thursday, December 22, 2011 - link
Why in the heck would they mention Linux drivers and their issues in an article covering the (paper) release and preliminary benchmarking of AMD's new graphics cards? It has nada to do with the subject at hand.Besides, hardly anyone cares, and those that do care already know.
chiddy - Thursday, December 22, 2011 - link
And I guess that AMD GPUs are sold as "Windows Only"?Thanks for your informative insight.
MrSpadge - Thursday, December 22, 2011 - link
There are no games for *nix and everything always depends on your distribution. The problems are so diverse and numerous.. it would take an entire article to briefly touch this field.Exagerating, but I really wouldn't be interested in endless *nix troubleshooting. Hell, I can't even get nVidia 2D acceleration in CentOS..
chiddy - Thursday, December 22, 2011 - link
You have a valid point on that front and I agree, nor would I expect such an article any time soon.However, on the other hand, one would at the very least expect a GPU using manufacturer released drivers to load a usable desktop. This is an issue that was distro agnostic and instantly noticeable, and only affected AMD hardware, as do most *nix GPU driver issues!
If all that was done during a new GPU review was fire it up in any *nix distribution of choice for just a few minutes (even Ubuntu as I think its the most popular at the moment) to ensure that the basics work it would still be a great help.
I will have to accept though that there is precious little interest!
Ryan Smith - Thursday, December 22, 2011 - link
Hi Chiddy;It's a fair request, so I'll give you a fair answer.
The fact of the matter is that Linux drivers are not a top priority for either NVIDIA or AMD. Neither party makes Linux drivers available for our launch reviews, so I wouldn't be able to test new cards at launch. Not to speak for either company, but how many users are shelling out $550 to run Linux? Cards like the 7970 have a very specifically defined role: Windows gaming video card, and their actions reflect this.
At best we'd be able to look at these issues at some point after the launch when AMD or NVIDIA have added support for the new product to their respective Linux drivers. But that far after the product's launch and for such a small category of users (there just aren't many desktop Linux users these days), I'm not sure it would be worth the effort on our part.
chiddy - Friday, December 23, 2011 - link
Hi Ryan,Thanks very much for taking the time to respond. I fully appreciate your position, particularly as the posts above very much corroborate the lack of interest!
Thanks again for the response, I very much appreciate the hard work yourself and the rest of the AT team are doing, and its quality speaks for itself in the steady increase in readers over the years.
If you do however ever find the time to do a brief piece on *nix GPU support after launch of the next generation nVidia and AMD GPUs that would be wonderful - and even though one would definately not buy a top level GPU for *nix, it would very much help those of us who are dual booting (in my case Windows for gaming / Scientific Linux for work), and somewhat remove the guessing game during purchase time. If not though I fully understand :-).
Regards,
Ali
CeriseCogburn - Thursday, March 8, 2012 - link
Nvidia consistenly wins over and over again in this area, so it's "of no interest", like PhysX...AmdInside - Thursday, December 22, 2011 - link
I won't be getting much sleep tonight since that article took a long time to read (can't imagine how long it must have taken to write up). Great article as usual. While it has some very nice features, all in all, it doesn't make me regret my purchase of a Geforce GTX 580 a couple of months ago. Especially since I mainly picked it up for Battlefield 3.ET - Thursday, December 22, 2011 - link
The Cayman GPU's got quite a performance boost from drivers over time, gaining on NVIDIA's GPU since their launce. The difference in architecture between the 79x0 and 69x0 is higher than the 69x0 and 58x0, so I'm sure there's quite a bit of room for performance improvement in games.Have to say though that I really hope AMD stops increasing the card size each generation.