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Atmega Speeds

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There are several atmega chips used with Arduino, the 328, 324, 1284,2560.

Generally lead to believe the 2560 is bigger and faster, yet looking at the specs they all state 1mips per 1mhz, so are they really all the same speed or are we missing some key point ?


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They are all 1mips per MHz but they run at different MHz. Depending of the board it's either 8 or 16 MHz. Some of the other compatible boards (not atmega) run much faster - Arduino Due = 84MHz. Wemos = 80/160 MHz. The Wemos mini is one of my favourites due to built in wifi and they cost me around US$5.



Active Member
Some Assembler Instructions of an AVR need more then 1 Clock.
Which they are You can see in in Chapter Instructions of the choosen AVR Datasheet.
The maximum clock speed depends from supply voltage and the choosen controller Type.
A-Types often go up to 20MHz Controller Clock at 5V supply.

You have to look very close which type works with the target clock speed of Your application.
The differnce can be only 1 character.

At an Arduino Board the voltage and clock is fixed, so there should be no troubles.


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There 3 8 mhz , 16 mhz and 20 mhz the 16 is a uno the 8 on nano and pro the 20 is on some clones.
The mega is 16

The best place to find out about the arduino is here https://www.arduino.cc/en/Main/Products

I like the esp2866 wifi comes in handy and it's easy to use with arduino ide.

Nigel Goodwin

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The Arduino ProMini (very small and useful) is 16MHz for the 5V version, and 8MHz for the 3.3V version, as the processor is only rated for 8MHz at 3.3V - presumably the Nano mentioned above is only 3.3V?.


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Lot of clones use the same 8 mhz bootloader on pro and the nano but it's all about voltage.
there is a new atmega328pb
Speed Grade: – 0 - 4MHz @ 1.8 - 5.5V – 0 - 10MHz @ 2.7 - 5.5.V – 0 - 20MHz @ 4.5 - 5.5V

Funny tho this the atmega 328p
Speed Grade: – 0 - 4MHz @ 1.8 - 5.5V – 0 - 10MHz @ 2.7 - 5.5V – 0 - 20MHz @ 4.5 - 5.5V

The mega 2560 can only go to 16 mhz
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