What is meant by "1 SPE is locked-out to help improve manufacturing yields"?

http://en.wikipedia.org/wiki/Cell_microprocessor#Commercialization
you see?what they mean by "1 SPE is locked out during test process to help improve manufacturing yields"?also does the PS3's cell cpu have 1 PPU+7 SPEs or 1 PPU+6 SPEs?
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