AMD's Radeon HD 6970 & Radeon HD 6950: Paving The Future For AMD
by Ryan Smith on December 15, 2010 12:01 AM ESTCayman: The Last 32nm Castaway
With the launch of the Barts GPU and the 6800 series, we touched on the fact that AMD was counting on the 32nm process to give them a half-node shrink to take them in to 2011. When TSMC fell behind schedule on the 40nm process, and then the 32nm process before canceling it outright, AMD had to start moving on plans for a new generation of 40nm products instead.
The 32nm predecessor of Barts was among the earlier projects to be sent to 40nm. This was due to the fact that before 32nm was even canceled, TSMC’s pricing was going to make 32nm more expensive per transistor than 40nm, a problem for a mid-range part where AMD has specific margins they’d like to hit. Had Barts been made on the 32nm process as projected, it would have been more expensive to make than on the 40nm process, even though the 32nm version would be smaller. Thus 32nm was uneconomical for gaming GPUs, and Barts was moved to the 40nm process.
Cayman on the other hand was going to be a high-end part. Certainly being uneconomical is undesirable, but high-end parts carry high margins, especially if they can be sold in the professional market as compute products (just ask NVIDIA). As such, while Barts went to 40nm, Cayman’s predecessor stayed on the 32nm process until the very end. The Cayman team did begin planning to move back to 40nm before TSMC officially canceled the 32nm process, but if AMD had a choice at the time they would have rather had Cayman on the 32nm process.
As a result the Cayman we’re seeing today is not what AMD originally envisioned as a 32nm part. AMD won’t tell us everything that they had to give up to create the 40nm Cayman (there has to be a few surprises for 28nm) but we do know a few things. First and foremost was size; AMD’s small die strategy is not dead, but getting the boot from the 32nm process does take the wind out of it. At 389mm2 Cayman is the largest AMD GPU since the disastrous R600, and well off the sub-300mm2 size that the small die strategy dictates. In terms of efficient usage of space though AMD is doing quite well; Cayman has 2.64 billion transistors, 500mil more than Cypress. AMD was able to pack 29% more transistors in only 16% more space.
Even then, just reaching that die size is a compromise between features and production costs. AMD didn’t simply settle for a larger GPU, but they had to give up some things to keep it from being even larger. SIMDs were on the chopping block; 32nm Cayman would have had more SIMDs for more performance. Features were also lost, and this is where AMD is keeping mum. We know PCI Express 3.0 functionality was scheduled for the 32nm part, where AMD had to give up their PCIe 3.0 controller for a smaller 2.1 controller to make up for their die size difference. This in all honesty may have worked out better for them: PCIe 3.0 ended up being delayed until November, so suitable motherboards are still at least months away.
The end result is that Cayman as we know it is a compromise to make it happen on 40nm. AMD got their new VLIW4 architecture, but they had to give up performance and an unknown number of features to get there. On the flip side this will make 28nm all the more interesting, as we’ll get to see many of the features that were supposed to make it for 2010 but never arrived.
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mac2j - Wednesday, December 15, 2010 - link
Um - if you have the money for a 580 ... pick up another $80-100 and get 2 x 6950 - you'll get nearly the best possible performance on the market at a similar cost.Also I agree that Nvidia will push the 580 price down as much as possible... the problem is that if you believe all of the admittedly "unofficial" breakdowns ... it costs Nvidia 1.5-2x as much to make a 580 as it costs AMD to make a 6970.
So its hard to be sure how far Nvidia can push down the price on the 580 before it ceases to become profitable - my guess is they'll focus on making a 565 type card which has almost 570 performance but for a manufacturing cost closer to what a 460 runs them.
fausto412 - Wednesday, December 15, 2010 - link
yeah. AMD let us down on this here product. We see what gtx580 is and what 6970 is...i would say if you planning to spend 500...the gtx580 is worth it.truepurple - Wednesday, December 15, 2010 - link
"support for color correction in linear space"What does that mean?
Ryan Smith - Wednesday, December 15, 2010 - link
There are two common ways to represent color, linear and gamma.Linear: Used for rendering an image. More generally linear has a simple, fixed relationship between X and Y, such that if you drew the relationship it would be a straight line. A linear system is easy to work with because of the simple relationship.
Gamma: Used for final display purposes. It's a non-linear colorspace that was originally used because CRTs are inherently non-linear devices. If you drew out the relationship, it would be a curved line. The 5000 series is unable to apply color correction in linear space and has to apply it in gamma space, which for the purposes of color correction is not as accurate.
IceDread - Wednesday, December 15, 2010 - link
Yet again we do not get to see hd 5970 in crossfire despite it being a single card! Is this an nvidia site?Anyway, for those of you who do want to see those results, here is a link to a professional Swedish site!
http://www.sweclockers.com/recension/13175-amd-rad...
Maybe there is some google translation available or so if you want to understand more than the charts shows.
medi01 - Wednesday, December 15, 2010 - link
Wow, 5970 in crossfire consumes less than 580 in SLI.http://www.sweclockers.com/recension/13175-amd-rad...
ggathagan - Wednesday, December 15, 2010 - link
Absolutely!!!There's no way on God's green earth that Anandtech doesn't currently have a pair of 5970's on hand, so that MUST be the reason.
I'll go talk to Anand and Ryan right now!!!!
Oh, wait, they're on a conference call with Huang Jen-Hsun.....
I'd like to note that I do not believe Anadtech ever did a test of two 5970's, so it's somewhat difficult to supply non-existent into any review.
Ryan did a single card test in November 2009.That is the only review I've found of any 5970's on the site.
vectorm12 - Wednesday, December 15, 2010 - link
I was not aware of the fact that the 32nm process had been canned completely and was still expecting the 6970 to blow the 580 out of the water.Although we can't possibly know and are unlikely to ever find out what cayman at 32nm would have performed like I suspect AMD had to give up a good chunk of performance to fit it on the 389mm^2 40nm die.
This really makes my choice easy as I'll pickup another cheap 5870 and run my system in CF.
I think I'll be able to live with the performance until the refreshed cayman/next gen GPUs are ready for prime time.
Ryan: I'd really like to see what ighashgpu can do with the new 6970 cards though. Although you produce a few GPGPU charts I feel like none of them really represent the real "number-crunching" performance of the 6970/6950.
Ivan has already posted his analysis in his blog and it seems like the change from LWIV5 to LWIV4 made a negligible impact at the most. However I'd really love to see ighashgpu included in future GPU tests to test new GPUs and architectures.
Thanks for the site and keep up the work guys!
slagar - Wednesday, December 15, 2010 - link
Gaming seems to be in the process of bursting its own bubble. Graphics of games isn't keeping up with the hardware (unless you cound gaming on 6 monitors) because most developers are still targeting consoles with much older technology.Consoles won't upgrade for a few more years, and even then, I'm wondering how far we are from "the final console generation". Visual improvements in graphics are becoming quite incremental, so it's harder to "wow" consumers into buying your product, and the costs for developers is increasing, so it's becoming harder for developers to meet these standards. Tools will always improve and make things easier and more streamlined over time I suppose, but still... it's going to be an interesting decade ahead of us :)
darckhart - Wednesday, December 15, 2010 - link
that's not entirely true. the hardware now allows not only insanely high resolutions, but it also lets those of us with more stringent IQ requirements (large custom texture mods, SSAA modes, etc) to run at acceptable framerates at high res in intense action spots.