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Jim Kahle：We have a 65 nanometer part
 Jim Kahle is the chief architect of the Cell microprocessor and the visionary behind the multiprocessing beast that is the heart of the PlayStation 3. He led IBM's side of the chip alliance with Sony and Toshiba. He has been designing microprocessors since the 1980s and was one of the founding members of the Somerset Design Center, the chip design house formed by Apple, Motorola and IBM at the onset of the Power PC alliance. He was also the chief architect of IBM's Power 4 microprocessor which was used in IBM servers and Apple's G5 Macintosh machines. I caught up with him after his recent keynote at a Cadence Design Systems conference.
DT: It seems like you finished the Cell chip designs early. The first prototypes came out in 2004 and this is 2006. Did you still need a lot of development time after that first tape out?
JK: We used that first tape out to get the initial software up and running. There were modifications we did to the chip over time. The design center is still active and participating. Our roadmap shows we are continuing down the cost reduction path. We have a 65 nanometer part. We are continuing the cost reductions. We have another vector where we are going after more performance. We have talked about enhanced double-precision chips. Architecturally we have double precision but we will fully exploit that capability from a performance point of view. That will be useful in high-performance computing and open another set of markets.
DT: That sounds like it’s not a PlayStation 3 chip?
JK: Yeah, it is a different vector. For us to extrapolate. We will push the number of special processing units. By 2010, we will shoot for a teraflop on a chip. I think it establishes there is a roadmap. We want to invest in it. For those that want to invest in the software, it shows that there is life in this architecture as we continue to move forward.
DT: Right now you’re at 200 gigaflops?
JK: We’re in the low 200s now.
DT: So that is five times faster by 2010?
JK: Four or five times faster. Yes, you basically need about 32 special processing units.
DT: AMD bought ATI Technologies and they signaled that a combined CPU and graphics processor is not so far off. They are going to do an initial crack at it for emerging markets in 2007. Is that something you see coming and is Cell anticipating this world already?
JK: If you look at a gaming system, there is obviously a close relationship between graphics and the main processing elements. Over time we will look to see how effectively we can make the main processor and graphics tie together. I won’t go beyond that.
DT: With Cell and PlayStation 3, was there a lot of thought about whether you needed a graphics chip?
JK: We explored that to understand the bounds of what we could do with the architecture. If you look at some of our ray tracing, ray casting techniques, they are very effective. People have worked on some software caches to help out the ray tracing. I wouldn’t say that is graphics processing because ray tracing is a little different. We’ve explored the bounds on this to understand where it can contribute with pure graphics processing. Over time, we have been exploring that.
DT: With Moore’s Law, is it inevitable that they will wind up on one chip?
JK: If you look at the PlayStation 2, eventually the graphics did get integrated into the Emotion Engine. Sony has talked about that. Definitely from a cost reduction view. Now we have to look at it from a performance point of view too. That is something we have to study for the future. Even beyond PlayStation 3. I don’t know if it is inevitable. We have to understand the pros and cons of it
http://blogs.mercurynews.com/aei/2006/10/the_playstation.html |
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