Big CPUs / GPUs already have physical redundancy, and a way to cut / rewire a limited amount of faulty parts by laser etching in the die, prior to packaging.
Cell processors are interesting because they do quite a bit of binning on a user facing SPI slave. You shift a thousand or so bit payload into it from a support/binrg up processor that tells it which pieces are disabled, how the PLLs are configured, etc.
Hacked PS3s could reenable the binned off 8th SPE for instance.
