i need to overclock an Arduino Uno to 30Mhz , pleaze consider this

Other Hardware General Electronics
21

When I overclock, I go up in steps of 2 MHz until the AVR will no longer run my extensive test code, which exercises every byte of SRAM, IO Pin, and uses the entire Flash. I do not check EEPROM, as this is the only weak point. I also test at least 10 of the same part.

When I hit the limit, I then drop down a "reasonable" amount to be "safe".
For ATTiny and ATMega88-328, this "safe" limit is 36MHz.

If you want to really push it, then at 5.5v, 40MHz is no issue.

Here is an ATTiny85 shoveling out 184x240 VGA at 36MHz!...

XMega is even better, with an easy reach of 64MHz.

Some may say it is absolutely insane to overclock to these limits, but that's fine.
I am in fact insane!

Just look at the results though... totally worth it!

Cheers!
Brad

22

Some may say it is absolutely insane to overclock to these limits, but that's fine.
I am in fact insane!

No you are not insane but just very silly. There is no point in doing this as there are processors available that can do that within the limits set by the manufacturers.

Just look at the results though... totally worth it!

Nothing like self delusion is there.

until the AVR will no longer run my extensive test code,

I doubt that your extensive test code is as extensive as you might think. It is not only the memory, which I suspect is only tested cursory, it is also all the instructions in the instruction set.

I suspect you think you are being big and clever but you don't impress me. Even dragging up this long dead post to boast about it shows a certain immaturity.

23

You have a suitable moniker indeed, Mike!

"Immaturity"... old enough to know better, but young enough to try anyway.
Yeah... I concur there.

Brad

24

Is the crystal you have a fundamental mode crystal or an overtone crystal.
The pierce oscillator in an Uno wont run at the correct frequency with an overtone crystal.
30 Mhz fundamental mode crystals are not common.

25

polymorph:
Why not just get a Teensy 3.1 for less than $20? 48MHz, overclockable to 96MHz. And lots more stuff like increased program and RAM space, built-in 12 bit DAC, etc.

Teensy 3.2 & 3.1: New Features

That was going to be my suggestion as well. I think standard is 72MHz on the Teensy 3.1/3.2, but the overclock to 96MHz is pretty much considered standard.

People are reporting stable operation as high as 168MHz if you need extra.

Ian.

26

Op, you should use the teensy or a stm32 maple for the job.
Edit: maple mini is very cheap.

27

mauried:
Is the crystal you have a fundamental mode crystal or an overtone crystal.
The pierce oscillator in an Uno wont run at the correct frequency with an overtone crystal.
30 Mhz fundamental mode crystals are not common.

I always use a clock oscillator.
On the 20MHz rated AVRs, I have found that overclocking beyond 25MHz is not stable unless you drive a clock signal into XTAL1. This makes a huge difference.

Indeed, there are so many high speed options available, from ARM to CPLD, but my goal was to see how far I could push an AVR. Just a fun project, but it was quite surprising that most would happily run at 36Mhz.

The XMega reaches 64MHz (2x overclock) without any issues, and I have had the XMega-384 up to 72 MHz, doing 640x480 VGA.

Again... just for fun.
Is it ok to have some fun, Mike?

Cheers!
Brad

28

Imo, overclocking is fun too.

29

Do you notice the chips feeling any warmer when overclocked?
How much of the functionality of the chip have you tried at the higher speeds?

30

check - http://garagelab.com/profiles/blogs/atmega328-overclock-30mhz

or this - Arduino overclocking with Liquid Nitrogen cooling 65.3Mhz@-196°C - YouTube

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C'mon rob... use html code tags... :o

32

CrossRoads:
Do you notice the chips feeling any warmer when overclocked?
How much of the functionality of the chip have you tried at the higher speeds?

No heat whatsoever.

I work on many projects at once in my lab, and often leave the overclocked video generators running for months. The ATTiny-85 has been going at 40MHz since November, and the XMega running at 65MHz... I can't remember the last time I turned off the power to that side of my bench!

There is no spectacular flash-bang when you reach the limit. Usually what happens is the AVR begins to reset at a high rate. Sometimes it will even work at some harmonic. The 328 actually runs stable on a 60MHz clock oscillator, but only at 20Mhz.

I have not done a lot with over-volting yet though.
XMega does fine at 5v, but this does not improve the top overclocking speed.

I have heard that ATMega will do better between 5.5v and 6.0v, and I may test this soon.
Already getting 36MHz out of 'em, so I am happy with the results.

ATMega-644 and 1284 are the worst, with 25 Mhz being the "safe" top end.
Those 2 start to drop out at around 28 MHz.

Does the Arduino use a real clock or an Xtal?
I have never seen one, but know the Uno has a 328, which is why I chimed in here.
If it only has an Xtal, you would have to feed a real clock into Pin B.6.

Digikey has every possible frequency available, and you can order pre-programmed cans for a few bucks.

Here is a thread I started on AVRFreaks that will detail my 36MHz adventures with the ATMega-328...

http://www.avrfreaks.net/forum/quark-328-single-chip-184x160-vga-game-system-atmega-328

Again Mike, before you start shaking your cane... I am just having fun, so chill dude!

Brad