An 8-core Cell procesor die
Cell processor reliability details may surprise you
As Sony's PlayStation 3 console nears its official release, more focus has turned to the technical wizardry that lays inside the actual machine. The Cell processor, developed by IBM, Sony and Toshiba, has gained a great deal of attention over the last year. In an interview with Electronic News however, IBM vice president of Semiconductor and Technology Services Tom Reeves says that his company is lucky if it can get 10% to 20% yields on the Cell processor.
The Cell processor is so complex that IBM even accepts chips that have only four out of the eight cores working. Not all cores end up functional says Reeves. In regards to why the yields are so low, Reeves says "[defects becomes a bigger problem the bigger the chip is. With chips that are one-by-one and silicon germanium, we can get yields of 95 percent. With a chip like the Cell processor, you’re lucky to get 10 or 20 percent. If you put logic redundancy on it, you can double that." According to Reeves, Sony will be using Cell processors whether they have all cores functional or not. Reeves says that the PlayStation 3 requires at least seven of the eight cores operational.
According to Reeves, IBM is still debating whether or not to discard the processors that have only six or less cores operational. Because of the design, the processors are still operational and can be used for various applications. IBM says that it will reserve the top chips for applications such as medical imaging and defense applications.
With Reeves' statements, it appears as though Sony will be producing PlayStation 3 consoles with different Cell processors -- some with all eight cores operational and some with just seven. Reeves however does not believe that Sony will offer different pricing for the machines and only time will tell if there will be performance differences. Reeves says however that users will not see any differences in speed. "The PlayStation 3 only uses seven of [the eight cores]. You'd have a spare."
In the interview, Reeves also talks about failure rate as there is a possibility that one of the cores in the Cell will "blow" at any given time. Reeves says that usually, testing during fabrication stages will detect whether a core or more will be problematic. Using electrical "fuses", IBM can "blow" out a core during wafer testing. When asked what would happen if a 7-core PlayStation 3 ends up losing another core during operation, Reeves stated that the user would simply send the unit back for replacement. Unfortunately, this only applies if the console is still under warranty -- if it isn't, the console is dead.
Over the last several months, speculation over the PlayStation 3's official retail costs have caused many gamers to sit up and take notice. Some analysts believe that Sony's new toy will cost too much to compete but Sony has said that the entry price will not affect the PlayStation 3's adoption. Considering the extremely low yields on the Cell processor in conjunction with extensive testing time to make sure final PlayStation 3 consoles ship with reliable processors, the high introductory pricing of the PlayStation 3 begins to show its true reasons. Sony Computer Entertainment Inc. (SCEI) president Ken Kutaragi previously said that if the PlayStation 3 was priced at $599, it would actually be "too cheap."
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