Most people seem to be excessively worried about overclocking. I will be happy to overclock my
720Mhz-rated Pandora up to 1.2Ghz, but I will do it safely.
My N900 has the same OMAP3 SoC, but according to that table, it's rated for only 600Mhz. Maybe I got lucky, but my N900 runs happily at 1150Mhz for hours, under heavy load. The popular maemo.org 'power kernel' manages dynamic clock speed and voltage, depending on the load. It uses a lower voltage than normal at low and regular clock speeds, without any problems, and uses a higher voltage at top speed, also without any crashes or glitches.
The smaller N900 phone gets
slightly warm after an hour running at top speed, playing HD movies. I think that this
slight warmth is not dangerous. It is certainly not getting to anything like the typical running temperature of a Pentium II chip, let alone those P4 chips that require some serious cooling machinery to survive. And the ARM silicon is supposed to be able to handle well over 100C without problems.
ARM chips have been running at dynamic clock speeds with dynamic voltage for 10 years, e.g. Intel's ARM5 X-Scale. They are designed to do this, and they do it very well.
What we need, to avoid any chance of damage to the core, is a monitoring / alarm system which watches the temperature sensors, and alerts the user or slows down if the CPU is getting hot. It could also keep track of the average clock speed, to ensure that the CPU has not been running full-throttle for too long. This can be configured for the user's preferences, whether for unmitigated speed or absolute safety.
A safety system like this could make it very safe to overclock with a top speed of 1150Mhz, without damaging the CPU at all.
As I understand the "5 years" is 5 years running 24/7 at top speed, without any rest. That would be equivalent to perhaps 100 years of real time for a pocket computer, given my usage patterns, need to sleep, work and play elsewhere. I doubt I'll outlive my Pandora's CPU.
If you have a performance car, do you drive by holding the accelerator flat to the floor until it reaches 400km/h, then keeping it at full throttle all the time while you're driving? No, you use full acceleration only from time to time when you need it. The same is true with our ARM SoC. You use top speed during a compile or intermittently when running a demanding game or watching an HD movie - the CPU should have some idle time between frames, and even a very big compile will be done in 10 to 15 minutes. Unless you intend to harness the thing in a compute-cluster, it will be switched off, suspended, idle or running slacking at low Mhz perhaps 80% of the time. It's not going to get hot.
In the unlikely worst case scenario, you can write Craig to send you a replacement board, perhaps it will come with a newer CPU. $100 every 5 years, it's No Big Deal.
When you need a burst of speed to overtake those lame cookie-cutter phones with their under-clocked CPUs and tiny batteries, you can ramp it up to 1.2GHz for a few minutes or half an hour. It won't crash, and in my opinion damage is avoidable by monitoring, and very unlikely in any case.
Sam
