This are hypothetical questions, as I have no urge to blow up my computer.
What would be safer/last longer with Overclocking, a top one(3GHZ) versus, say, a lower end(450MHZ)? Ie, less likelier to fry, might last longer…
Is it possible to overclock with little chance to fry it(maybe only a few extra MHZ)?
What’s the highest you can overclock(not regarding safety or how long it’d last), at any range? How does it change over the lower/higher range?
Generally, overclockers want the earliest models of any given line. Why? Because the manufacturing process isn’t debugged yet, so they don’t know how fast is too fast for any given chip. Therefore, they set the speed limiters to a lowest common denominator they know every chip off the line will be able to handle. If you get a relatively good chip, you could get good speed increases out of it for relatively little extra cost without waiting for the manufacturing process to be fixed. Or you could fry the silicon and end up with a useless piece of crap.
(I don’t do it, and I don’t know how to. Google indexes good overclocking FAQs.)
Generally, you get the largest overclocks as a % of clock speed from mid end chips, from a certain chip line, especially after a couple months of chip manufactoring. For example, you would probably be able to overclock a 2.4Ghz Pentium4C much more than a 3.2Ghz one. You see, a 2.4Ghz chip and a 3.2 Ghz chip with the same CPU core are in fact made on the same lines; the chips are tested and the better chips get marked as 3.2 Ghz ones; some can only run 2.4Ghz and get sold as those. As the process matures, you have more and more chips being able to run at higher speeds, but due to the higher demand for lower end chips, you will see chips that could run at 2.8 or 3.0 Ghz getting sold as 2.4Ghz chips, making overclocking them very easy and safe to do. Though it is a matter of luck of getting a good chip.
Generally, the less you over clock, the less chance of frying; every chip I have seen will overclock as least a little. Even then, if you set it too high, most of the time your computer will just refuse to boot; a simple reset of CMOS will fix it. I have gone though this quite a bit, trying to get my chip to run faster, while still being stable. Make sure you have lots of cooling; this greatly aids your speed.
Even my Athlon 2000XP Palomino core can overclock from 1.67Ghz, to 1.73Ghz, though it runs a little hot. Note that the AthlonXP comes in 4 different core revisions, each running at a variety of clockspeeds/ratings. The Pentium4 also has a couple of different cores available, though I am not familar with them, and will only explain the AthlonXP ones.
Their is the Palomino core, which is the oldest, and ran from 1500rating/1.33Ghz to 2100rating/1.73Ghz; this core runs the hottest, and doesn’t overclock well; you probably won’t find many of these.
Then there is the Thoughbred A core, which had some heat problems, and is pretty rare. It was replaced by the
Thoughbred B series which goes from, IIRC, 1700rating to 2800 rating. These chips overclock quite well; I have heard of plenty of people getting $50 Athlon 1800 chips to run at 2400 or 2600 speeds.
Finally, there is the Barton cored chips, which have double the L2 cache. They come in 2500 to 3200 ratings, and they also overclock quite nicely. I have heard of plenty of people getting $80 2500 Bartons to run at 3000 or 3200 speeds.
Now, AMD has just released its Athlon64 chips, which are 64 bit chips, but I couldn’t tell you how well they overclock.
As for your last question, the highest possible overclock depends greatly on both the individual chip used, as well as your cooling method. I have seen places on the web where they have gotten 3.2Ghz Pentium4s overclocked up near 5Ghz; they were using liquid nitrogen for cooling though, making it somewhat impractical for actual use.