I remember quite a few years ago when overclocking was really just emerging, there were many reports that overclocking is quite harmful for your CPU - whether it was from the heat or higher voltages.
Do you believe that it is still the case now ? - CPU manufacturers are much more open towards the concept now - but has that come through in their product design. With modern cooling systems and motherboard designs, is overclocking still significantly harmful over the usable life of the component ? (i.e before it becomes obsolete )
if your like average joe who replaces his pc envery 2-3 years then there is no harm in mild overclocking, but if you want to keep it for alot longer or shorter then you just adjust how much voltage u use and temps etc.
As long as you keep voltages low and your hardware cool, overclocking should not decrease the life of your hardware to the point of replacement before it's obsolete. Now this isn't to say that you won't kill your motherboard when overclocking for the first time, but if you are intelligent and do your research, you should be able to use decent overclocks without regret.
Say your using a I7 920, comes stock at 2.6 would last probably 10 years, but you would never use it for 10 years since it will be obsolete in probably 4-5 years, overclocking it to 3.6-4.0 would drop it down to maybe 7 years.
This is all speculation, but you see the point that it will usually be obsolete before your overclock affects your total use of the hardware.
Back 10 or so years ago, I built a box with a late model P233MMX. This was back when you had to physically jumper a block of pins to set CPU core speed. After about a year, I bumped the speed up to 266 MHz. - it ran fine. After another year - onward to 300 MHz. I found an S370 HSF for it. It ran fine. I started experimenting with undocumented jumper settings. I found a jumper setting that would allow the CPU to run at 333 MHz.
I discarded the still working motherboard last summer.
---------- Overclocking since 1978 - Z80 (TRS-80) from 1.77 MHz to 2.01 MHz
There is a possiblity of harming it if you go to an extreme. Just a little overclocking typicly wont hurt much. You must have proper cooling though. If cooling isn't good enough, then your just trying to set it on fire.
Intel also has their extreme line. (like the Core 2 Duo Extreme) They can be overclocked to a much greater speed, but do require more cooling. (I recommend water cooling) I'm sure AMD has a simular line of CPUs.
Mil Spec 217 i think is the one for reliability. they developed the spec based on loads of empirical data, and found that the life of IC's generally is shortened by high heat (in the range of above 85 degrees C junction temp).
however, i don't know of any empirical tests involving enough CPU's to be statistically meaningful.
in any case, in the past i've been paid to keep temps low on various military programs, working as a design engineer on R&D teams. there seemed to be agreement between the EE's, quality engineers, etc. that they wanted help keeping their IC's running cool(er).
i think when you're in the range of 30-50 degrees C junction temps, you don't have much to worry about. below some threshold, the temperature doesn't hurt them.
If you keep the CPU adequately cooled it isn't. But if the CPU gets to hot to long then long term damage will occur. But the manufacturers are taking overclocking into design perspective. When only the most hardcore enthusiasts were doing it, many small computer stores were taking older slower CPU's and overclocking them and selling them as higher value chips when they were really more dangerous cause people were not cooling them enough. So for a while people were selling motherboard with locked multipliers so you couldn't overclock a CPU. Then once people were able to tel the difference and the marketing ploy was no longer good... companies began to openly accept overclocking.