The RV770 Story: Documenting ATI's Road to Success
by Anand Lal Shimpi on December 2, 2008 12:00 AM EST- Posted in
- GPUs
Just One Small Problem: We Need a New Memory Technology
The R600 GPU had an incredibly wide 512-bit memory interface, the problem with such a large interface is that it artificially makes your die bigger as you’ve got to route those interface pads to the memory devices on the board. For RV770 to have the die size ATI wanted, it needed to have a 256-bit memory interface, but using (at the time) current memory technology that wouldn’t give the GPU enough memory bandwidth to hit the performance targets ATI wanted.
When the options were either make the chip too big or make the performance too low, ATI looked elsewhere: let’s use a new memory technology. Again, put yourself in ATI’s shoes, the time was 2005 and ATI had just decided to completely throw away the past few years of how-to-win-the-GPU-race and on top of that, even if the strategy were to succeed it would depend on a memory technology that hadn't even been prototyped yet.
The spec wasn’t finalized for GDDR5 at the time, there were no test devices, no interface design, nothing. Just an idea that at some point, there would be memory that could offer twice the bandwidth per pin of GDDR3, which would give ATI the bandwidth of a 512-bit bus, but with a physical 256-bit bus. It’s exactly what ATI needed, so it’s exactly what ATI decided to go with.
Unfortunately whether or not GDDR5 shipped by the summer of 2008 wasn’t all up to ATI, the memory manufacturers themselves had a lot of work to do. ATI committed a lot of resources both monetarily and engineering to working with its memory partners to make sure that not only was the spec ready, but that memory was ready, performing well and available by the summer of 2008. Note that the RV770 was going to be the only GPU that would use GDDR5, meaning that it was ATI and ATI alone driving the accelerated roadmap for this memory technology. It’s akin to you trying to single handedly bring 100Mbps internet to your city; it’ll happen eventually, but if you want it done on your time table you’re going to have to pickup a shovel and start burying a lot of your own cable.
ATI did much of the heavy lifting with the move to GDDR5, and it was risky because even if RV770 worked out perfectly but the memory wasn’t ready in time the GPU would get delayed. RV770 was married to GDDR5 memory, there was no other option, if in three years GDDR5 didn’t ship or had problems, then ATI would not only have no high end GPU, but it would have no performance GPU to sell into the market.
If GDDR5 did work out, then it meant that RV770 could succeed and that it would be another thing that NVIDIA didn’t have at launch. That is, of course, assuming that ATI’s smaller-die strategy would actually work...
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Chainlink - Saturday, December 6, 2008 - link
I've followed Anandtech for many years but never felt the need to respond to posts or reviews. I've always used anandtech as THE source of information for tech reviews and I just wanted to show my appreciation for this article.Following the graphics industry is certainly a challenge, I think I've owned most of the major cards mentioned in this insitful article. But to learn some of the background of why AMD/ATI made some of the decisions they did is just AWESOME.
I've always been AMD for CPU (won a XP1800+ at the Philly zoo!!!) and a mix of the red and green for GPUs. But I'm glad to see AMD back on track in both CPU and GPU especially (I actually have stock in them :/).
Thanks Anand for the best article I've read anywhere, it actually made me sign up to post this!
pyrosity - Saturday, December 6, 2008 - link
Anand & Co., AMD & Co.,Thank you. I'm not too much into following hardware these days but this article was interesting, informative, and insightful. You all have my appreciation for what amounts to a unique, humanizing story that feels like a diamond in the rough (not to say AT is "the rough," but perhaps the sea of reviews, charts, benchmarking--things that are so temporal).
Flyboy27 - Friday, December 5, 2008 - link
Amazing that you got to sit down with these folks. Great article. This is why I visit anandtech.com!BenSkywalker - Friday, December 5, 2008 - link
Is the ~$550 price point seen on ATi's current high end part evidence of them making their GPUs for the masses? If this entrire strategy is as exceptional as this article makes it out to be, and this was an effort to honestly give high end performance to the masses then why no lengthy conversation of how ATi currently offers, by a hefty margin, the most expensive graphics cards on the market? You even present the slide that demonstrates the key to obtaining the high end was scalability, yet you fail to discuss how their pricing structure is the same one nVidia was using, they simply chose to use two smaller GPUs in the place of one monolithic part. Not saying there is anything wrong with their approach at all- but your implication that it was a choice made around a populist mindset is quite out of place, and by a wide margin. They have the fastest part out, and they are charging a hefty premium for it. Wrong in any way? Absolutely not. An overall approach that has the same impact that nV or 3dfx before them had on consumers? Absolutely. Nothing remotely populist about it.From an engineering angle, it is very interesting how you gloss over the impact that 55nm had for ATi versus nVidia and in turn how this current direction will hold up when they are not dealing with a build process advantage. It also was interesting that quite a bit of time was given to the advantages that ATi's approach had over nV's in terms of costs, yet ATi's margins remain well behind that of nVidia's(not included in the article). All of these factors could have easily been left out of the article altogether and you could have left it as an article about the development of the RV770 from a human interest perspective.
This article could have been a lot better as a straight human interest fluff piece, by half bringing in some elements that are favorable to the direction of the article while leaving out any analysis from an engineering or business perspective from an objective standpoint this reads a lot more like a press release then journalism.
Garson007 - Friday, December 5, 2008 - link
Never in the article did it say anything about ATI turning socialistic. All it did mention was that they designed a performance card instead of an enthusiast one. How they approach to finally get to the enthusiast block, and how much it is priced, is completely irrelevant to the fact that they designed a performance card. This also allowed ATI to bring better graphics to lower priced segments because the relative scaling was much less than nVidia -still- has to undertake.The built process was mentioned. It is completely nVidia's prerogative to ignore a certain process until they create the architecture that works on one they already know; you are bringing up a coulda/woulda/shoulda situation around nVidia's strategy - when it means nothing to the current end-user. The future after all, is the future.
I'd respectfully disagree about the journalism statement, as I believe this to be a much higher form of journalism than a lot of what happens on the internet these days.
I'd also disagree with the people who say that AMD is any less secretive or anything. Looking in the article there is no real information in it which could disadvantage them in any way; all this article revealed about AMD is a more human side to the inner workings.
Thank you AMD for making this article possible, hopefully others will follow suit.
travbrad - Friday, December 5, 2008 - link
This was a really cool and interesting article, thanks for writing it. :)However there was one glaring flaw I noticed: "The Radeon 8500 wasn’t good at all; there was just no beating NVIDIA’s GeForce4, the Ti 4200 did well in the mainstream market and the Ti 4600 was king of the high end. "
That is a very misleading and flat-out false statement. The Radeon 8500 was launched in October 2001, and the Geforce 4 was launched in April 2002 (that's a 7 month difference). I would certainly hope a card launched more than half a year later was faster.
The Radeon 8500 was up against the Geforce3 when it was launched. It was generally as fast/faster than the similarly priced Ti200, and only a bit slower than the more expensive Ti500. Hardly what I would call "not good at all". Admittedly it wasn't nearly as popular as the Geforce3, but popularity != performance.
7Enigma - Friday, December 5, 2008 - link
That's all I have to say. As near to perfection as you can get in an article.hanstollo - Friday, December 5, 2008 - link
Hello, I've been visiting your site for about a year now and just wanted to let you know I'm really impressed with all of the work you guys do. Thank you so much for this article as i feel i really learned a whole lot from it. It was well written and kept me engaged. I had never heard of concepts like harvesting and repairability. I had no idea that three years went into designing this GPU. I love keeping up with hardware and really trust and admire your site. Thank you for taking the time to write this article.dvinnen - Friday, December 5, 2008 - link
Been reading this site for going on 8 years now and this article ranks up there with your best ever. As I've grown older and games have taken a back seat I find articles like this much more interesting. When a new product comes out I find myself reading the forwards and architectural bits of the articles and skipping over all the graphs to the conclusions.Anyways, just wish I was one of those brilliant programmers who was skilled enough to do massively parallelized programming.
quanta - Friday, December 5, 2008 - link
While the RV770 engineers may not have GDDR5 SDRAM to play with during its development, ATI can already use the GDDR4 SDRAM, which already has the memory bandwidth doubling that of GDDR5 SDRAM, AND it was already used in Radeon X1900 (R580+) cores. If there was any bandwidth superiority over NVIDIA, it was because of NVIDIA's refusal to switch to GDDR4, not lack of technology.