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[Editorial]
Stack 'Em High and Sell 'Em Cheap ...Well, Maybe
Paul Whytock
ED Online ID #16737
May 24, 2007
Much like car parks that become more efficient if vehicles can be stacked in a multi-story configuration, the same is true for memory chips.
Chip stacking is not a new concept. A few years ago, Intel announced a packaging system with the snappy little title of “Ultra-Thin Stacked Chip Scale Package.” It allowed the stacking of a maximum of five memory chips on top of each other. A year later, Intel unveiled a chip with 80 processing cores that could handle an impressive trillion calculations per second that employed stacking technology.
Now, after nearly 10 years of research and development, IBM has joined the chipstacking fraternity. The company says it’s confident that this is the way to power future supercomputers, and I think IBM is absolutely right on.
Very cleverly, IBM has developed technology that obsoletes the wires typically used to connect stacked chips. So how are the stacked chips connected? The answer is that holes are made through the silicon dies and the chips are connected by tungsten-filled vias that are etched through the silicon. Intel’s teraflop device used a similar idea.
So why all the excitement? The reasons are numerous. Chip stacking will undoubtedly accelerate the processing speed of chips, with the added operational advantage that it may also help battle heat dissipation—the eternal enemy of increased processing capabilities. Chip efficiency is expected to get a 40% boost and, of course, there’s the space-saving advantage that’s always important for those manufacturers of mobile phones and other handhelds.
So it’s not surprising, then, that IBM was prepared to invest many years of R&D time and money. And its good to see the company is now reaping the rewards, some of which may well prove to have great value in other IBM product areas.
IBM is considering using stacking technology in its multicore processors. The reason is because vertical stacking will allow for the delivery of uniform power to each of the stacked chips.
As more and more cores are added to chips, it becomes increasingly difficult to deliver uniform power to each one. By stacking them vertically and reducing the length of the connections between them, IBM hopes to overcome this problem.
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