Sunday, September 30, 2012

Ask James Reinders: Multicore vs. Manycore

Leading edge insight and explanation from James Reinders, Director, Software Evangelist, Intel Corporation. Conducted by Geeknet Contributing Editors Jeff Cogswell and John Jainschigg.
Go Parallel: You talk about Multicore vs. Manycore.  Are those separate technologies?
James Reinders:  Yeah, they’re not necessarily the most perfectly defined items. I would define them by saying Multicore really started in earnest around 2005, and it’s been an incremental approach to putting on a chip designs that were already in small computers.  We used to have computers with two or four processors in them; now we have them on a single chip. Multicore seems rather incremental.
Manycore represents a little different concept. What  if you’re willing to put a lot more cores on a single device, what changes? Two things change: One, you have this revelation that you’re going to be highly parallel. And so the way you design the hardware also changes  because you start to optimize assuming only parallel programs. The the other thing that changes is the software has to be parallel. I sometimes call these highly-parallel devices. We have the Intel MIC architecture which realizes this concept, and the Intel Xeon coprocessor
It’s a variable argument in computer architecture; there’s no right answer.  Do you want a small number of really powerful processors or a large number of less-powerful ones?
There’s great research that’s gone on in this area for decades, going back to one of the earliest papers, a   thesis by Danny Hillis  who eventually founded Thinking Machines Corporation and built the Connection Machine parallel supercomputer. With that particular machine, I would say one of the lessons in it was that they went too far being simple. Too many things  were simple, and they had to evolve their architecture. They definitely went the direction of adding more capabilities until eventually, like many startups, they failed as a business are largely looked at as creating a lot of brilliant people and technology. 
In any case, it’s an exploration, and to this day we’re still exploring the problem. And there isn’t a right answer. It depends so much on what you’re trying to do and actually having that breadth is very valuable for the industry to have different capabilities to match different needs.
Interviews are edited lightly for brevity and clarity.
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