Continue to Site

Welcome to

Welcome to our site! is an international Electronics Discussion Forum focused on EDA software, circuits, schematics, books, theory, papers, asic, pld, 8051, DSP, Network, RF, Analog Design, PCB, Service Manuals... and a whole lot more! To participate you need to register. Registration is free. Click here to register now.

Microcontroller & overclock

Not open for further replies.


Newbie level 6
Feb 20, 2002
Reaction score
Trophy points
Activity points
Hi, i'm kinda new on all this stuff, i was wondering, speaking of microcontrollers is there anything like "overclocking", let's say i have this ATMega103 that runs at 6Mhz but i put a 10Mhz crystal on it, would it work at 10Mhz or just blow up?

Thanks in advance
Tomas Diaz

I am also wondering about what will hapen if I put a 12MHz crystal on MSP430F149,(normaly 8MHz) will it still work properly? will it affect the reliability if it seems to work at first?

Overclocking does work with 8051. I have tested with Atmel 89C51 devices with 50% overclocking. The circuit has not failed so far.

Generally overclocking a microcontroller doesn't generate a problem, until a certain percentage of course.

The manufacturers guarantee what they have their parts tested for, although they can be quite conservative sometimes.

The issue is though that what seems to work fine in the LAB is not guaranteed to work well in a product, over the complete temperature range etc.

So if you are going to overclock a micro board as a test in the LAB there is no problem, but if you intend to do it in a final design that's going to the market then I wouldn't suggest it.

Hi, i'm kinda new on all this stuff, i was wondering, speaking of microcontrollers is there anything like "overclocking", let's say i have this ATMega103 that runs at 6Mhz but i put a 10Mhz crystal on it, would it work at 10Mhz or just blow up?

Neither, nor. It won't execute the correct code because the on-chip flash would not deliver the instructions fast enough.

Check out the new ATmega128 part, it runs at 16 MHz and replaces the ATmega103.


You can think about overclocking as about resistor overloading.

For example you can overload 0.25 W resistor with 2W. After some time you will have smoke on that resitor.

So you can put fan on it and solve power disipation problem. If you need more than one resistor you can put fan on every resistor and get resistor & fan network.

If you need more power on resistor just put more fans. This is overclocking philosophy.

My 10% rule for overclock:

10% higher clock with
10% higher supply voltage
under twice more heat sink surface and
twice the airflow

I know that u can overclock a 80C166 with 24MHz Crystal. Yes, the chip will become hot...

If u know that u have an asynchron uC-design, it should be overclocked easily.

Mostly not the complete chip goes mad, but if there is a PLL or anything other analog part this will have a problem...

Theres no problem at all with overclocking, except this: if you overclock a chip forget the specifications. You can also try to use the microcontroller with other temperatures, the manufacture specification is relevant for all devices. So most of them work in worser ambiental conditions.

Hi all
I developed mcu several years ago using CMOS technology. From my understanding you can use m@ximum supply voltage(Vcc) and at highest temperature of the mcu circumstances say 70 deg.c. and input the clock signal from specified value to higher frequency.
you may sure that the load capacitance must be m@ximum. And you will get highest clock frequency on that mcu.

Microcontrollers (well, some anyway) CAN be overclocked to very high levels and still work reliably.

This is due to:

-small die size and high %% od speed reserve.
This is not an Athlon, which heats as a small powerplant. PIC12C5xx, 16Fxx and similar are small beasts, which do not run into serous thermal problem when overclocked.

-Microcontrollers are made to work in quite wide voltage conditions. So, if it has to run at 2.7-5.5V at specified clock freq. it will have speed problem at 2.7V-if anywhere.

If you can guarantee narrower voltage supply region at the upper region (like 5-5.5V), you might be able to make it run at significantly higher freq.

-Many models have internal oscillator for external quartz, which might fail to run reliably with much faster quartz.
Usually one can tweak external components or just plug in external clock signal.

After this also the declared temperature range might be a problem, so don't rely for it to work at full industrial temperature range, but near room temperatures should be O.K.

All said goes for homebrewing, not proffesional use.

I have toyed with 12C509 and had it run at 16 MHz, and also had decent results with a few PIC16F84 and all Atmel's AVR's I could find.

Other part of the story is that it is almost never needed, well I didn't need it.

Usually one needs special clock rate to match some baud rate etc.- not very high clock rate.

Almost always I found that rethinking code can be greater satisfaction and bring you greater speed improvement than simple throthling RPMs...

Not open for further replies.

Part and Inventory Search

Welcome to