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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pastyface - Wednesday, December 3, 2008 - link
Great job on the article! Generally today's reviews consist of me quickly going to the benchmarks portion and seeing if a new game was used or if any screwy results came out. This article however was much different. You had my attention from the get go and I didn't take a break in my reading until the whole article was finished.It is a real shame that so much of the work in reviews are overlooked in favor of simple graphs but this article was different and I thank you for that.
MarchTheMonth - Wednesday, December 3, 2008 - link
I really enjoyed the read, and it really gives me an appreciation for the card i just happen to get (hd 4850).I may not speak for others, but these are the kind of articles I like to read, the kind that really explain in detail what's really happening. Anand, you did an excellent job of giving perspective (be in ATI's shoes in 2007 when nvidia was doing this...etc) to the article that gave definition between the "so obvious" hindsight we have now to the "this is suicide!" view that it must have seemed like to be there in 2005.
Now, for my own counter-perspective, I can understand why AMD, Intel, and nVidia may not do this very often. On the flip side of the coin, I'm not a mainstream user, and I don't exactly build 1000s of computers that ATI can sell. Bottom line speaking, a story that's interesting to me, I don't bring them $$$$. And on top of that, this story is also giving a lot of info to the competition, which can be at best a double edged sword, and at worst too much information to be self-destructive.
belladog - Wednesday, December 3, 2008 - link
Excellent article, we love this stuff. Benchmarks gets a bit boring after a while.I wonder what affect if any, the revelations about price fixing(between ATI and Nvidia) had on the pricing of the RV770 GPU's??
I mean if the lawyers hadnt broken up the party maybe the 4870 could have been $80-$100 dearer?
Anyway, interesting article.
Griswold - Wednesday, December 3, 2008 - link
The price fixing took part before AMD bought ATI. And it would be safe to assume that it stopped at the latest at that time, but it probably did stop well before that (the earliest evidence is an e-mail from 2002). AMD should know better than to point the finger at Intel and do something that is equally wrong in another segment of their business.feelingshorter - Wednesday, December 3, 2008 - link
Keep up the good work and never let the haters get you down! There's always people b!tching when they don't know how hard it is to write well (any moron can "write"). But its good stories like this that has been the bread and butter of Anandtech.
The pressure of deadlines, writer's block, or not having enough to write. I appreciate what you do and I know its stressful at times. Others can sympathize but I can empathize having been an amateur journalist myself (in high school and at the university newspaper).
san1s - Wednesday, December 3, 2008 - link
If this article was about an nvidia GPU then the ati fanboys would proclaim it reeks of bias.good article though anamdtech
Adul - Wednesday, December 3, 2008 - link
That was one of the best article I read in a while. It was very enjoyable to get an idea of how things are worked out years in advanced of when the product launches.This was a huge gamble on AMD/ATI part. My hats off to them for having the balls to do something different.
dani31 - Wednesday, December 3, 2008 - link
Speaking of AMD, it would have been nice to have more insight on how the acquisition of ATI fitted in the design process.But this topic seems to have been deliberately omitted in this article.
JonnyDough - Wednesday, December 3, 2008 - link
Maybe that's because the interviewed the ATI chip designers and not the AMD head haunchos? Just a thought.lifeobry - Wednesday, December 3, 2008 - link
Really fascinating article. The amount of work put into creating these cards and the competition between the two companies is compelling stuff.