Use more freq than max supported Processor frequency

[fireball003]

Hi,
What goes wrong when more frequency crystal is used than maximum supported processor frequency?

For example ARM7TDMI based processor NXP LPC2103 supports highest 70 MHz frequency. But if I use a 100 MHz crystal , then what will happen? What will go wrong?

The purpose of my question is- the frequency boundary set for a perticular core is the limitation of the core architecture? or the limitaiton is of the silicon used?

If frequency is incresed more than the maximum supported value of the core then does the operations go wrong? Or, the CPU burns or stops working anyway???

Thanks in advance.

 

[Old Nick]

Timing errors, overheating are the main problems. You might squeeze upto 20% extra from a processor (on a good day with the wind at your back), but you could drastically reduce its operating life.

 

[fireball003]

so timing errors are handled at the processor? Is there any effect on pipelining ? Is that also handled by the built in functionality of the processor? Which part handle there errors?

Thanks a lot.

 

[Old Nick]

In general errors are not handled in a processor, what happens if a timming errors (or any errors)occur is that external controllers etc (memory controllers, bus controllers etc) don't get the information they expect/need to function correctly (or at all), and the system fails in some way.

 

[ldanielrosa]

The best that could happen is that the increased frequency increases the current proportionally, and is nothing more than a thermal problem that can be handled by rigorous attention to intake v. dissipation.

A sneakier and more problematic failure is that the instruction codes will not process correctly and the chip goes insane.

Between those extremes you must accept that some modules may fail while the rest of the uC is running well.

Bottom line is that beyond the maximum frequency the microcontroller is not guaranteed to fail, it just isn't guaranteed to work.