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AMD Radeon HD 7970 3GB Graphics Card Review - Tahiti at 28nm

Author: Ryan Shrout
Manufacturer: AMD

Tessellation, Texture Filtering, Compute Architecture and Media Processing

Along with these compute and architecture changes come quite a few additional performance improvements starting with tessellation.  When NVIDIA introduced Fermi to the world it far exceeded the tessellation performance that AMD offered in their Radeon 5000 series of cards and while both Barts (6800) and Cayman (6900) architectures improved it, NVIDIA still holds a pretty dramatic lead.  

Southern Islands looks to improve on tessellation performance by a factor of 4x while not "wasting die space" as they claim NVIDIA has done.

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The 9th generation tessellation engine from AMD, built inside the dual geometry engines, improves performance with off-chip buffers and slightly larger caches.  The changes AMD has made will improve tessellation at each factor (used to determine tessellation levels) and in many cases, the performance difference is notable. 

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AMD has provided a graph that demonstrates the scaling ability of the new tessellation engine on Southern Islands when compared to the Radeon HD 6970.  Raw tessellation rates have increased from 1.6x to 4x with the majority of the improvement found after a tessellation factor of 9 or 10.  Games and applications that utilize tessellation heavily, like Unigine Heaven, Lost Planet 2 and Crysis 2, see jumps from 55% to 139% in relative performance.

Whether or not this is enough to catch the current generation of GTX 580 designs has yet to be seen though with an obvious improvement in pixel shading power as well (with 2048 SPs), the Radeon HD 7970 will obviously become a performance leader. 

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Being as upfront and honest as they tend to be, AMD discussed their texture filtering quality quite a bit at the technology day in Austin last month.  Improvements in the algorithm have greatly reduced the shimmering artifacts seen on certain textures without having to blur it.  AMD claims that this is all done without any performance penalty and is a result of simple adjustments on their end - no major hardware changes were needed.  

The Southern Islands as a Compute Architecture

Even though AMD was focused nearly completely on the SI architecture as a gaming platform, there is no denying that many of the architectural changes made were the first step in progressing AMD towards a more heterogeneous computing environment.  That is after all, the primary goal of the Fusion System Architecture (FSA) detailed by Demers at AFDS this June.

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SI has a pair of Asynchronous Compute Engines (ACE) that allow for independent scheduling and work dispatch which will improve multi-tasking efficiency and context switching as well.  These engines can operate in parallel with the graphics command processor essentially allowing SI-based parts to work on two varying workloads at the same time.  The matching pair of DMA engines can actually completely saturate a PCI Express 3.0 x16 connection with 16 GB/s of bidirectional bandwidth.

As Josh discussed in his original analysis, AMD has the ability to adjust the ratio of single precision to double precision performance on Southern Islands and for their consumer level graphics cards they have chosen a 4:1 mix.  While the 7970 is capable of 3.79 TFLOPS of compute, it can handle only 947 GFLOPS of double precision.  Because of the move to a vector+scalar architecture though reaching higher utilization of that processing power should be easier for software developers. 

The GPU has full ECC protection for DRAM and SRAM and is the first to offer support for OpenCL 1.2, DirectCompute 11.1 and C++ AMP .

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Finally, rounding out the new architecture changes is an improved media processing feature that improves performance on SADs - sum of absolute differences.  This operation is important for video and image processing algorithms like the one used in AMD's own SteadyVideo technology.  With the Radeon HD 7970 this new QSAD option allows the GPU to handle more than 513 billion calculations per second to keep up with real time playback and adjustment of 1080p 60 FPS content.  AMD claims this performance allows the HD 7970 to operate at a 10x performance improvement compared to the company's own Phenom II X4 980 processor.

December 21, 2011 | 09:15 PM - Posted by wargames12

If it's faster that the 580, it kind of makes sense that it costs a bit more. It's pretty disappointing to see the prices of current gen cards stay so high for so long though. Hopefully when we see Nvidia's new card we'll see some price drops all around on the current generation.

December 21, 2011 | 09:40 PM - Posted by Mr_Tea (not verified)

My thoughts exactly. I was hoping to see AMD drive the performance/dollar up with this release. At this rate single GPUs will be launching at $1000 in 2 years :(

December 21, 2011 | 09:47 PM - Posted by wargames12

I want to blame the rich guys who will actually pay the extra 2-300 dollars for the extra 10-20 percent performance, but I can't. I would do the same if I had the extra cash haha.

December 26, 2011 | 07:49 AM - Posted by Anonymous (not verified)

That is pretty funny! You obviously don't remember how much the 8800GTX and Ultra cost when they were launched. I paid $950.00 for my first 8800GTX. With the price drop just go Crossfire it keeps getting better and better, as well as cheaper.

January 3, 2014 | 08:21 AM - Posted by Anonymous (not verified)

Ha, turns out you were right.

December 21, 2011 | 09:57 PM - Posted by Ryan Shrout

I'm glad that point came across well in my review. I love the performance out of this, but I guess I just expected/wanted AMD to undercut NVIDIA to put pressure on them and start the price wars again.

There is still a chance that NVIDIA cuts the GTX 580 down to $425 or something - they have a lot of room with the GTX 570 priced at $340. If they do that, then AMD will have to drop the 7970 price.

December 21, 2011 | 09:51 PM - Posted by Buyers

Good solid review. I think i was hoping for a little more of a performance increase over the 580. I look forward to seeing eyefinity benchmarks with this card with crossfire setup.

Couple of edits:
Page 3, talking about DDMA:Multi-tasking under image of triple screen gaming with soccer on background tv:"With the Radeon HD 7970 it is not possible to both play a game and..." should that be now, given the way the rest of the sentence and paragraph read?

Metro 2033 @ 1920x1080 line graph X-axis labels are the default Series1/2/3/4 instead of the gpu name labels.

December 21, 2011 | 09:56 PM - Posted by Tim Verry

Yes, it is now possible.

December 21, 2011 | 09:58 PM - Posted by Ryan Shrout

Yeah, thanks for that type - kind of a big difference. :)

And also, yes, we are looking forward to doing both Eyefinity and CrossFire testing very soon!

Let me know if there are particular titles you want to see tested!

December 23, 2011 | 03:01 PM - Posted by Nacelle (not verified)

I'm sure it goes without saying BF3 in Eyefinity is what everyone wants. Not much else brings two 6970's to a crawl.

December 21, 2011 | 09:57 PM - Posted by Slash3 (not verified)

Would it be possible to disable vsync on Skyrim and re-run your tests? There are several methods which successfully disable it, including editing the .cfg file (iPresentInterval=0) or using a utility like Radpro to force vsync disable on the process. As it stands, that particular game's set of benchmarks is totally useless. Nice card, though.

December 21, 2011 | 10:00 PM - Posted by Ryan Shrout

Based on my research and testing, I wasn't able to find a way to do disable Vsync with AMD cards without modding the game, which seems less than ideal.

If you have a link to a solution though directly, I'll gladly try it!

December 21, 2011 | 10:10 PM - Posted by Kennneth (not verified)

Who are you going to believe?

http://nl.hardware.info/reviews/2472/32/amd-radeon-hd-7970-review-dirt-3...

December 21, 2011 | 10:13 PM - Posted by Mr_Tea (not verified)

I saw a slide that showed this card doing separate audio out to each display and intelligently switching if a video was moved to another display. Any truth to that? Testing? That would be pretty awesome. Thanks.

December 21, 2011 | 10:19 PM - Posted by Mr_Tea (not verified)

Whoops, must have skipped that page.

June 12, 2013 | 11:33 PM - Posted by Launa (not verified)

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December 21, 2011 | 10:25 PM - Posted by RashyNuke (not verified)

Ryan what is with porn music...Oh found my 7970 wetspot.

December 21, 2011 | 10:31 PM - Posted by jstnomega (not verified)

given the current state of the art re Vid games, isn't it all still a matter of pushing pixels? if that's the case, then clearly something aint right here - look at the 40nm vs 28nm Pixel Fillrate figures in Ryan's video - barely any gain at all

December 21, 2011 | 10:46 PM - Posted by Ryan Shrout

Pixel fill rate is not really the defining factor right now. It is not how many pixels you can push its what you calculate on those pixels in real-time. Shading power! Oh, and geometry is picking up again in importance.

December 21, 2011 | 11:25 PM - Posted by Anonymous (not verified)

Great review, its nice to see someone actually moving the technology along, and innovating. Seamlessly it seems, this time.

December 22, 2011 | 07:26 AM - Posted by Ryan Shrout

Agreed. More than than a year with the GTX 6970 and GTX 580 is enough for me.

December 22, 2011 | 12:05 AM - Posted by bjv2370

good review

December 22, 2011 | 01:52 AM - Posted by Irishgamer01

This card is way over priced.
I for one will be sticking to my current setups. For now.
The sweet spot for this level of card is 399.
While performance is better its not enough for me.
I want to see Nvidia's offering. If they hold their current pricing structure, match or better performance, then AMD will be punished big time.

Will give me a certain amount of pleasure, as I hate price milking, just because they can.

December 22, 2011 | 07:27 AM - Posted by Ryan Shrout

Yes, what NVIDIA has to say about GPUs in the next few months will be very important here. Curious to see if Kepler will hold up to its promises.

December 22, 2011 | 03:36 AM - Posted by Metwinge (not verified)

I shall be placing my 2 5870's for one of these as im very impressed by these benchmark scores especially in BF3 as thats the game im playing atm. I have 2 1080p monitors sitting under our tree so i can see these cards taking a bashing with the few high end games i play

Thanks for the excellent review Ryan

December 22, 2011 | 07:27 AM - Posted by Ryan Shrout

Thanks!

And have fun with Eyefinity!

December 22, 2011 | 05:37 AM - Posted by Kevin (not verified)

Great review, but I cant see spending upwards of $600 for it =/

December 22, 2011 | 05:44 AM - Posted by Apostrophe (not verified)

It is a lovely video card - shame the price is a bit high. I do hope Nvidia responds with something equally impressive. 2012 is going to be interesting.

By the way, have you guys considered adding Star Wars: The Old Republic to your battery of tests? It's the biggest MMO to launch in years and I would expect that a large portion of your readers will be interested.

December 22, 2011 | 07:28 AM - Posted by Ryan Shrout

We did consider it, but didn't have to validate before this article. We still might, depending on how GPU-bound the game is, if it all.

December 22, 2011 | 05:56 AM - Posted by nabokovfan87

Extremely glad the GCN architecture Isn't as terrible as bulldozer ended up. I went to the skyrim page first and was waiting for a huge dissapointment, but yeah.

I am intrigued to see how my box will handle the new card. I have an MSI 4850 512mb and am upgrading to the next card made by the 48xx series team. Sort of amazing to think of the differences in performance is going to be 5-10x better when comparing raw specifications alone.

If anyone is interested I will be doing some benchmarks and testing things out, if PCPER wants to use those for a writeup or discuss it, I would be more then happy to provide it and listen to your thoughts.

CANNOT WAIT!

ALSO: There are a lot of people waiting to upgrade, waiting for the "new stuff" from either to decide on what to do, that is why the pricing is so high right away. Like I said above and I am sure many others will be grabbing the 4950, it is more about upgrading then it is price. These cards last 3-4 years, and the price initially is worth it for the upgrade possibilities and expanded feature set then what is currently available in terms of power usage, temperature, performance, and so on.

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