so i want the arduino uno to operate at30Mhz , i released a video output library lately and getting a 30mhz clock speed can ramp the resolution up pretty much really good .
i do have a 30Mhz crystal and a Atmega328 with arduino bootloader .
the questions are :
-can i get a stable system ?
-should i operate the ardunio at 6V or 5V ? i heard 6.2v is needed for 30Mhz ?
-can i operate the system at room temp- at 30Mhz wich is 27°C in average or should i apply cooling ?
thank you very much
-can i get a stable system ?
No idea but probably not.
-should i operate the ardunio at 6V
No
Look doing anything outside the specifications of a chip is a stupid thing. This whole over clocking business came about because some manufacturers had different speed grades of processor that you paid a premium for. In reality as their fabrication improved there were not enough of the lower speed grade to meet demand so they sold some devices as the lower speed grade. This gave some people the idea that any chip could be over clocked successfully. The chip in the Arduino Uno has a different speed grade but this is lower at 10MHz so it is unlikely that you could get anything working reliably at a faster speed.
Any way how are you going to know if it is working reliably? You would have to check all the processor instructions and timing at the maximum chip temperature you want to operate it at, and I don't think you have the equipment to do that.
If you want to have a processor with a faster clock then get a Due.
ok what about 20mhz , a guy told me once that ATM328 are made for 20mhz top
Well, that guy probably read the data sheet then:
Speed Grade:
0 - 4MHz@1.8 - 5.5V,
0 - 10MHz@2.7 - 5.5.V,
0 - 20MHz @ 4.5 - 5.5V
There have been plenty of threads about changes needed to the IDE files (boards.txt) and select code to run at that speed.
If you want a "processor" with faster speed, get a Pi.
;D i already have a PI dude . but i really like AVR micro-controllers and the arduino UNO and i want to work with these ones .
20Mhz would be enough . so 5.5volts eeh ? thank you 
There was another guy on the forums here who used external clocks (active oscillators and ext clock, not just the crystal) to overclock atmega's and said things worked up to around 30mhz. You should try to find his thread where he talked about it.
i released a video output library lately and getting a 30mhz clock speed can ramp the resolution up pretty much really good .
If it works for you, fine. For your own personal use, you can try anything! Have fun! Worst case, maybe you fry your Arduino. But, it would be a very bad idea to release a library to the public that requires another user to exceed the chip's specs.
It might work for you, but it might not work for other users. It's a statistical thing.... Maybe 9 out of 10, or maybe one out of 10 will work at 30mHz... Maybe one out of a million, or maybe none will work. Maybe you'll buy two or three and they are all out of the same batch and they all can be overclocked.... Then, you may never find one again that works when overclocked.
P.S.
I've worked for a couple of companies that were selecting/screening parts to use them outside of their specs. Maybe they start by throwing-away 10 or 20 percent of the parts (maybe even less). Then, the next batch may only half are "good", or maybe none are good and production gets shut-down in a panic until the thing is re-designed or another part is specified.
20Mhz would be enough . so 5.5volts eeh ? thank you
No use 5V as 5.5V is the absolute top and leaves no room for tolerance.
All the electrical specs are over the range 1.8V to 5.5V:
Common DC characteristics TA = -40C to 105C, VCC = 1.8V to 5.5V
Absolute Max is 6V.
Run at 5V to be compatible with any chips you might hook up.
uze45:
so i want the arduino uno to operate at30Mhz , i released a video output library lately and getting a 30mhz clock speed can ramp the resolution up pretty much really good .
i do have a 30Mhz crystal and a Atmega328 with arduino bootloader .
the questions are :-can i get a stable system ?
-should i operate the ardunio at 6V or 5V ? i heard 6.2v is needed for 30Mhz ?
-can i operate the system at room temp- at 30Mhz wich is 27°C in average or should i apply cooling ?
thank you very much
I've done a lot of testing in the area of overclocking the AVR chip. You cannot run it at 30 MHz... it won't work or if it does start, it won't be reliable.
The furthest you can push it and still have it be 100% stable is 22.1184 MHz. As far as cooling goes, this isn't a PC. Running at a higher clock speed won't make it hot, nor does it need any cooling.
Also note that at higher frequencies, you may no longer get away with sloppy wiring, long clipleads and proto-boards. You'll have to be a lot more careful in this area or else peripheral devices may not work (or may only work intermittently).
It may work but with an external canned oscillator (best with CMOS output level).
You have to set fuses for an external clock as well.
The 30MHz crystal will not work as all crystals beyond ~25MHz are 3rd overtone ones, so the chip's oscillator will run at 10MHz (1/3).
thank you very much guys . i already released the lib for 16Mhz and it works fine 176/224px PAL check it out if you want . so ima just overclock this one to 21mhz and operate at 5V .
i hope i can contribute to this forum the same way you guys do one day.
Overclocking...
http://forum.arduino.cc/index.php?topic=280417.0
These look germane...
http://forum.arduino.cc/index.php?topic=76020.0
http://forum.arduino.cc/index.php?topic=102181.0
pito:
It may work but with an external canned oscillator (best with CMOS output level).
You have to set fuses for an external clock as well.
The 30MHz crystal will not work as all crystals beyond ~25MHz are 3rd overtone ones, so the chip's oscillator will run at 10MHz (1/3).
Not all of them. The ones I experimented with are all fundamental (as high as 40 mhz).
uze45:
thank you very much guys . i already released the lib for 16Mhz and it works fine 176/224px PAL check it out if you want . so ima just overclock this one to 21mhz and operate at 5V .i hope i can contribute to this forum the same way you guys do one day.
21.1184 is the highest I would personally go. I tested a lot of boards and found that they all work reliably at that speed, but I wouldn't guarantee it for someone else.
A safer bet would be 18.432 (another nice integer dividable for baud rates speed) that's a little faster than 16 but not how wild.
Another speed tip... compile with the avg-gcc -Ofast option. It enables some non-standard features in the compiler and may break delay loops coded for -Os, but -Ofast is almost twice as fast as -Os in many places.
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.
I would never run a 328 at 30MHz.
I prefer 36MHz and 40MHz!...
Had an ATmega88 up to 45MHz as well, but the 328 wouldn't cut it beyond 42MHz reliably.
Brad
RadicalBrad:
I would never run a 328 at 30MHz.
I prefer 36MHz and 40MHz!...Had an ATmega88 up to 45MHz as well, but the 328 wouldn't cut it beyond 42MHz reliably.
Brad
damn , that response had an unexpected twist . that sounds interesting ... though i don't think it's safe , the manufacturer must've set that clock speed limit for a reason . i like this though ... i really do .