Got a Z170 Pro4S from ASRock. Got an i5 6500 for it, and i'm thinking about overclocking later on. But that is yet to be determined. I've seen people post their non-K Skylake overclocks, but there aren't many details. I'd like to know the overclocking threshold of those chips before increasing voltage is necessary to go any higher. My limits are basically the voltage. Once i need to start increasing it, even a tiny bit, that's where i would stop. Someone has already explained to me that voltage is a huge factor in CPU life, and heat is the obvious one. And the latter goes for all machines, basically.
I'd be really, really happy going to 4.0GHz or 4.2 as long as i can do so without touching the voltage. Now what i also want to touch on is the stress of overclocking and lifespan of such parts when overclocked. I've been listening to Carey Holzman a lot, and he is not a fan of overclocking. He has very good reasons for not wanting to overclock. Ultimately, though, he says that you're pushing the part beyond its limits from what the manufacturer intended it to be. Now what i'm trying to figure out is if this is just simply a person who has a very old school mentality (which is fine, mind you) or if what he says still holds true. I've learned that a great way to know a piece of hardware is ALWAYS to have a reference point. Using this alone, we can learn a lot about hardware. Why am i saying this? Well, i remember in the pre-Nehalem and Phenom II days, overclocking was a different story, and people tended to be a lot more weary about how much they're bumping up the frequency. Once we reached 45nm, especially from Intel, we saw incredible gains with just air cooling. It was really mind blowing. You could take a base Nehalem i7 920 and take it from 2.6Ghz to 4.0Ghz+ with ease.
Now, with Skylake at 14nm, is it safe to say that pushing an i5 6500 from 3.2 to 4.0 or 4.2GHz will not see as much stress as it did from the Nehalem's overclock situation? I always, ALWAYS like the idea of any machine working with clock-like precision, and being able to do so for a very, very long time. If something is put under stress it can't handle, i won't even mess with it. Also. If i go ahead and overclock said CPU, will the CPU still be able to dynamically change its frequency? or power saving modes such as C-States and whatnot (whatever those are)?
So I am fairly new to overclocking as I have only played with my FX 8350 for almost a year now and pushed it up to 4.65 GHz with a multi/fsb combo so I can't speak first hand for OCing on Intel. With that disclaimer out of the way, what I have understood is that while overclocking will reduce the lifespan of you CPU, more often than not you will be looking to replace the chip long before it dies as long as you are intelligent with your overclock.
Heat and Voltage are the two biggest killers of silicon chips as you mentioned. Obviously as you bump up the clock speed on a chip it will get a little warmer as it is "working harder". Heat will go up a significant amount as you bump the voltage and my FX chip seemed to hit the point at about 4.5 GHz where it needed twice as much voltage increase to stabilize as the last voltage bump and results in temps climbing very fast to go from 4.4-4.5-4.6 GHz.
My understanding (please feel free to correct me as I am still learning more about overclocking as I play with my machine everyday) is that if you only bump up the voltage one or two notches to stabilize your frequency increase your CPU should easily last 3+ years with out a question and arguably will last as long as it would have if left at stock speeds.
So with the non-K sku from Skylake, I believe you will have to do a FSB (Front Side Bus) or BLCK (Base Clock) overclock as the multi on your 6500 isn't unlocked. This is a little different from most of the overclocking that people do but it is still easy enough to find guides for.
I hope someone else can come fill in the info you are looking for as to how well the 6500 will OC. I am curious as my brother has one but he is not looking to OC it yet. More than likely it is just a lower binned 6600k and won't OC as well as the 6600k do but I would think you could at least bump it up to 3.6 GHz with a bump or two to the voltage. So it technically isn't any different from the 6600k other than the default Clock and Voltage. Binned chips will end up decreasing the spread of possible max and min overclock as Intel or AMD will test the chip and get a good estimate on how well it would overclock and then clock it higher and sell it for a few bucks more if they can.
Just make sure to keep a close eye on your temps as that is going to be the biggest threat to your CPU as you don't wish to change the voltage much.
TL:DR Watch your temps, keeps the Volts low and your CPU should be fine for a long time