The RV870 Story: AMD Showing up to the Fight
by Anand Lal Shimpi on February 14, 2010 12:00 AM EST- Posted in
- GPUs
Carrell Loses His Baby: Say Goodbye to Sideport
Sitting at dinner with Eric Demers and Carrell Killebrew is honestly one of the best experiences I’ve ever had working with ATI. Before he got huge and subsequently left, I used to have annual dinners with Pat Gelsinger at Intel. They were amazing. To get to sit at the same table as someone as talented and passionate as a Gelsinger, Demers or Killebrew is one of the most fortunate and cherished parts of my job.
Eric was telling me about how they trimmed down 870 from over 400mm2 down to 334mm2 and how wonderful the end product was. I stopped him and asked for more detail here. I wanted an example of a feature that they had to throw out but they really wanted to keep in. Manufacturers rarely tell you what they threw out, marketing likes to focus on what’s in the chip and make everything sound like a well calculated move. Thankfully, marketing wasn’t allowed to speak at my dinner.
Eric turned to Carrell and said: “i know one feature we could talk about.”
“Sideport”.
Carrell responded, “OH MY GOD, that’s totally not fair.” (note that Carrell does not sound like a teenage girl, imagine that phrase just spoken more engineer-y).
When ATI first talked about the Radeon HD 4870 X2 they told us about a feature called Sideport. It was a port off each RV770 GPU that could be used for GPU-to-GPU communication.
Sideport as it was intended to be used
The whole point of doing CrossFire in alternate frame rendering mode (AFR) is that the chips never have to talk. The minute you have to start synchronizing them, you kill performance. Sideport was supposed to alleviate that.
Unfortunately, due to power reasons, Sideport was never used on the 4870 X2. ATI’s reference design had it disabled and all vendors followed suit.
Sideport was Carrell Killebrew’s favorite feature, and he had to give it up.
In early 2008 ATI realized they had to cut this chip down from 20 - 22mm on a side to 18mm, everyone had to give up something. Carrell was the big advocate for making 870 smaller, he couldn’t be a hypocrite and not give anything up.
A bunch of my conversation with Carrell at this point had to go off the record. Sideport would have been useful in RV870, but it’s unfortunately not there. Although he did tell me not to be surprised if I saw Sideport again at some point. Carrell doesn’t give up easily.
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ThomasS31 - Monday, February 15, 2010 - link
...it would be very interesting if nVidia tell us the story openly, what happened with this long delayed newly designed chip.Anand staff, please try and persuade them to tell all details! :)
XiZeL - Monday, February 15, 2010 - link
dont want to look like a fanboy here but these stories just make me like ATI even more, make me feel like part of the familiy...why dont you guys ever write these about nVidia?
Anand Lal Shimpi - Monday, February 15, 2010 - link
The only reason I'm able to write something like this is because of how open/honest/unmarkety Carrell Killebrew is. And how trusting AMD PR is that they allow me to talk to him without any sort of limitations in place.Until recently, there hasn't been a similar contact for me at NVIDIA. That has changed in the past few months and I've already reached out to him to see if he is willing to allow me the same opportunity to talk about Fermi.
If I can make it happen, I will :)
Take care,
Anand
XiZeL - Tuesday, February 16, 2010 - link
thanks for the reply :)just for the record, as a costumer and someone who really likes technology, these kind of articles will help me take my final descision when bying a product...
yeally looking forward to seeing the same from Nvidia and try to understand their aproach on building a chip :)
thanks again
Mat3 - Monday, February 15, 2010 - link
I really enjoy reading stuff like this. One request for the next time you're talking to ATI guys: can you ask them about Fast14 and why it didn't work for them?Iketh - Monday, February 15, 2010 - link
6900 series = Pagan6800 series = Sarigan
6700 series = Saipan
6600/5500 series = Tinian
6400 series = Rota
Im probably way off lol
hyvonen - Monday, February 15, 2010 - link
Leaker! You'll be reported.XtremeOne - Monday, February 15, 2010 - link
Thank You for this beautiful and insightful article. Like many before me, i registered just to say that. Anandtech is one of the sites I fell very lucky to know about. Some of your articles are a bit "techie" for me, but this one is practically impossible to stop reading. :D Thank you Anand.Iketh - Monday, February 15, 2010 - link
it's a shame there cant be more articles like this... having a close relationship with one company allows it every year or two, but there are many companies in this field which could produce many more stories... i feel Anand is slowly tapping into a gold minejstall - Monday, February 15, 2010 - link
This is a fantastic article, nice to get some insight into the the RD and thought process just as much as it is to see performance charts. Be nice to see a little more of this.