Review Index:

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.

February 4, 2012 | 08:28 AM - Posted by SiliconDoc (not verified)

Gee Mark, telling the truth, while calling Nvidia "turtle!" a couple of times is shilling for the eeevil "them" ?
Is this place that much pop culture red amd fanboy that you have to excuse yourself even after calling Nvidia names?
It's a sad biased world when what is patently obvious to a truthful mind must be parsed and dissed just to try to get along and not be attacked.
I'm frankly sick of it.
It's okay ot say AMDATI is a copycat and came in late to superior Nvidia styled architecture and they will get beaten by Nvidia in the next release - it's OK to say it.
In fact, we've all probably heard the latter part already in leaked rumor - at which point, for those who keep up, the AMD fanboys went angry wild and screamed it was a group of Nvidia marketing team spammers who leaked $299 and faster... even though Charlie claimed he saw the benchmarks...
Well, in this case time will tell, and thanks for speaking your mind, and no thanks for calling Nvidia turtle twice, and don't apologize just because red fanboys will attack you, that is, if you can help yourself. Is it really that bad, the attacking of anyone who says a single bad word against AMD and has a good prediction for Nvidia that just makes sense based upon endless years of patterns...that you have to caveat some simple truths and cover the bases with some armor ?

December 23, 2011 | 03:04 PM - Posted by Stas (not verified)

From what I see, AMD takes over GTX580 by a ridiculous margin, being absurdly priced. Ryan, raise GTX580 gpu and memory clocks to meet HD 7970 ones, and GTX580 will show same or better performance. In the result, HD 7970 can be buried straight away.

February 4, 2012 | 08:36 AM - Posted by SiliconDoc (not verified)

That's an interesting thought. If that pans out, we shouldn't be hearing about "superior architecture" from those who promote AMD, endlessly, it seems.
However, they will just claim superior tech anyway and blame the "release" drivers and claim future releases will unleash the "true power". The next breath they will claim AMDATI no longer has driver issues and is now equivalent to Nvidia...
YES I say, let's see an apples clocks comparison.

December 24, 2011 | 11:13 AM - Posted by gabriel (not verified)

that makes my life even harder...

Now I don't know what to do, buy a 6990 or one 7970 and upgrade later by getting a second one, or even if I should wait for the 7990.

what do you guys think?

December 24, 2011 | 02:20 PM - Posted by Ryan Shrout

Hard to say - as I noted in my review, I almost always pick a single GPU over a dual-GPU solution if performance is close the same. Less hassle to deal with and fewer potential problems.

December 26, 2011 | 01:30 AM - Posted by Swoosh (not verified)

Since the release of AMD's 7900 series video cards is just
the corner, its best to wait for the release of the mighty
7990, so your options as far as future proof gaming will be
much longer and may infact (if you are using a single full HD
monitor) will never have to upgrade video card again because
that 7990 for sure is one helluva long, bad ass, intimidating,
very very fast video card that will give you the gaming
performance more than you expected and if you're into movie
editing, its performance (as far as openCL GPU acceleration
support is concerned) will even give you faster renderings
like never before that includes 3d renderings that supports
OpenCL. :-)

December 24, 2011 | 01:43 PM - Posted by Swede (not verified)

Great review!

Man, is there an easy way to get your hand on gfx cards in general and get them shipped overseas? As of right now the 580's are averaging at $680 over here (in Sweden) and I'd like to upgrade from my 5850.

December 26, 2011 | 01:34 AM - Posted by Swoosh (not verified)

Upgrading from 5850 to 7970?

Well, sounds like a very good upgrade decision for me!
go for it! :-)

December 26, 2011 | 09:05 PM - Posted by nabokovfan87

try amazon .uk/.de or somewhere

They have shipped stuff to me in the US, they might do it to your location as well. especially .uk to Sweden.

December 27, 2011 | 04:14 PM - Posted by Z (not verified)

HOW DO PEOPLE HAVE REVIEWS OUT ? the PROPER drivers for PCI-E Gen3 are not even out !-?

December 29, 2011 | 08:38 AM - Posted by Anonymous (not verified)

Just wondering how much WATTS does my power supply have to be to support it?

January 2, 2012 | 04:02 AM - Posted by crunzaty (not verified)

i think minimum is 450 Not quite sure ^^

January 2, 2012 | 04:01 AM - Posted by crunzaty (not verified)

I think nVIDIA will come with a new card that will beat this and be cheaper :)

January 9, 2012 | 09:02 AM - Posted by soldierguy

Hey mention a future review of Eyefinity/Crossfire...For sure I'd like to see that.
Nice review thanks.

January 18, 2012 | 01:04 PM - Posted by Anonymous (not verified)

This is a great card. I was a little hesitant to fire sale my 2 MSI 6970 Lightnings (which are amazing) and buying a single 7970, but it was unwarranted. The performance, once easily overclocked (by ATI/AMD's stock overdrive), is on par with my previous setup on games that supported crossfire. The games that didn't support it, well this card just blows my previous setup out of the water in that scenario.

Another point that ALMOST made me sit on my hands for a while and wait was going from top of the line custom cards (msi lightnings)to launch day OEM cards. I've only purchased cards with after market coolers for the past 3 generations but I just couldn't wait to try out the 7970. I'm happy to say that while gaming, I don't notice a difference in fan noise. If anything, it runs cooler than my previous setup (obviously crossfire had a lot to do with it) and it may be actually quieter. While the Lightnings had an excellent HSF along with all sorts of other custom parts, the 7970's 28nm process just really nullifies the need for a monster HSF setup.

Plenty of great reviews out there on the interwebz, go read those. Just wanted to 5 star this because of the fool with the 3 star review spreading FUD.

February 24, 2012 | 07:48 PM - Posted by Danny (not verified)

just a question..

i've bought one of this cards... but i have a problem. When i start gaming the Graphic card heats so much, over 70 degrees Celcios.

Any idea of what the problem?

October 8, 2012 | 10:20 AM - Posted by Anonymous (not verified)

but will it play Wolfenstein 3d in ultra settings. Just kidding this card rocks add a second card in xfire unstopable

July 12, 2013 | 09:52 PM - Posted by fake name forced me (not verified)

I get 10 or 20 fps of choppy, erratic performance in TF2 on w8000 in linux. A software renderer would probably be faster. The linux drivers are garbage.

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