After upgrade my CPU to an 840qm the bloq. mayus led blinks four times, wich means I have a problem "Graphics controller not functional". I think it is a problem that the CPU does not have integrated graphics, but in the manual of the laptop it indicates that this CPU is compatible.
Notebooks with the quad core processors use different motherboards than the ones with dual core processors.
See chapter 3, page 17, item 10...
(10) System board (includes replacement thermal material): For use only with Intel Core Quad processors 611348-001 For use only with Intel Core Dual and Core2 processors 599414-001 For use only with Intel Core Quad processors (1-GB) 622627-001 For use only with Intel Core Dual and Core2 processors 622626-001
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