the processor would slowly (over several months or even weeks) become more unstable over time with a degradation in maximum stable clock speed before dying and

the processor would slowly (over several months or even weeks) become more unstable over time with a degradation in maximum stable clock speed before dying and becoming totally unusable This is an electromigration[0] and/or hot carrier injection[1] problem. Both are exacerbated by temperature and voltage, but are not the reason chips are stuck at 3-4GHz. One actual limiter is pipeline depth. Deeper pipelines is an easy way to enable an increase in frequency. The problem in a nutshell- the longer the pipeline, the greater the overhead & the larger the penalty of branch misses. [0] http://en.wikipedia.org/wiki/Electromigration http://en.wikipedia.org/wiki/Electromigration [1] http://en.wikipedia.org/wiki/Hot-carrier_injection http://en.wikipedia.org/wiki/Hot-carrier_injection