'overclocking' a PIC ?

[RGBrainbow]

Hi,

is it possible to clock a 20MHz PIC with let's say 24MHz without negative effects?
Anyone who already tested that ?

regards
joachim

 

[Nigel Goodwin]

Hi,

is it possible to clock a 20MHz PIC with let's say 24MHz without negative effects?
Anyone who already tested that ?

I've never actually tried it with a 20MHz chip, but I have run 4MHz 16C84's at 12MHz quite happily. I can only suggest you try it and see, the only downside is it might reduce reliability.

 

[RGBrainbow]

Thank You. That sounds good. I'll give it a try and post the results.
regards
joachim

 

[Andy_123]

I think it depends on actual PIC:
I had a couple 18F242 with 12 Mhz crystal PLL mode at 48MHz.
It was working without any problems
One 16F870 20MHz was working at 24MHz also.

 

[motion]

I once had a need for 20MHz PIC16F877 parts. I was sent 4MHz ones instead. I tried them anyway in the meantime and all three samples worked at 20MHz.

 

[Nigel Goodwin]

I once had a need for 20MHz PIC16F877 parts. I was sent 4MHz ones instead. I tried them anyway in the meantime and all three samples worked at 20MHz.

I never even bother checking the numbers, they all seem to work equally well, I suspect they simply come off the same production line - perhaps they test them?, perhaps not?, but simply label some 4MHz and some 20MHz.

 

[evandude]

I work in the wafer sort area of a semiconductor manufacturing plant; that means we test all the chips when they are still die, as part of a silicon wafer.

In most cases, when there is one device that comes in several "flavors" based on performance, such as the rated frequency, it's all based on how the die tested out. They all come off the same wafer, it's just that the ones that have better test results will get labeled 20mhz, and the ones that don't will get labeled something lower. Same thing with computer processors. Often a part will run far over its rated speed, but it tends to suffer in SOME way that makes it fail a certain test. For hobbyist purposes, we'll probably never even notice that, as we aren't generally pushing our PICs to the absolute limits of their ratings in all categories.

 

[motion]

If one speed grade is 4Mhz and the next higher one is 20Mhz, there has to be plenty of room above 4Mhz.