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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DerekWilson - Thursday, December 4, 2008 - link
I'm glad you guys were able to stick to the plan an launch at the amazing prices you hit. It really shook up the industry and helped bring higher performance to lower price points. Now we just need the same thing to happen with integrated graphics.But seriously ... about those future architectures ... maybe you guys want to sit down and have another nice long chat? ;-)
tygrus - Thursday, December 4, 2008 - link
Choice A : Spend another 1B on a larger chip R&D, fab problems, low yields, high unit cost, potential delays, large dual-slot with space&cooling problems. Loose mid-range revenue potential, more R&D/time etc. to make half-size chip for mid-range.Choice B : Make the design to be price/power/performance efficient for very profitable mass-market. If you users want almost double the performance, buy 2 identical cards which saves on not producing a low volume BIG chip/card. (Though now we have 2 chips for X2 which still simplifies and reasonable efficient compared to a card design cramming a single BIG chip starved of bandwidth).
CloudFire - Thursday, December 4, 2008 - link
hands down one of the best, if not the best article i've ever read at anand. GREAT JOB! it shows how believing and getting back up when you're being beat down can get you where you want to be!for those people who took up the challenge to be different and change, imo are the true innovators who changes the world in the face of extreme adversity.
Emperor88 - Thursday, December 4, 2008 - link
Great artilce. There are precious few of these.Thanks a lot :)
cowofdoom - Thursday, December 4, 2008 - link
Long time reader, first time poster. Great article. I really think it says it all. Any time you get a chance to write articles like this I would love to see them. Great job.Emperor88 - Thursday, December 4, 2008 - link
haha first time (wait second now) poster here as well. Best article I've read here.Barack Obama - Thursday, December 4, 2008 - link
Keep it comin'!Boundless - Wednesday, December 3, 2008 - link
Very nice article once again...helps reinforce my decision of keeping this place readily bookmarked since I first visited back in 2001.Regs - Wednesday, December 3, 2008 - link
I want to know what AMD was thinking for those quite 3 years when they blew Prescott out of the water. Did they see Conroe coming? I think it's time for Anand to get on some black paint and go commando over there at AMD HQ.Cloudie - Wednesday, December 3, 2008 - link
One of the best articles I've ever read. Kudos to Anand, and thanks to AMD (: