Also, I believe the Uno32/PIC32 chips are 3.3V, but the pins are 5V "tolerant".
Correct? That's what you meant by 5V compatible.
Yep. I think this is a big deal for hobbyists, particularly the less technical
ones which is what Arduino is aimed at.
This means it will 'just work' with many 5v components
and you won't instantly blow up your board when you plug in a 5v shield
or hook it up to a 5v part that drives a high at 5v.
Just my personal opinion but I think creating a fairly expensive 3.3v board that is not 5v tolerant
like DUE for the Arduino crowd wasn't the best of ideas.
Given the lack of 5v tolerance, I think it was just plain dumb to handle the the voltages and IOREF the way
they did. I would have swapped IOREF and 5V. i.e. put the MCU voltage where the current 5V pin is
and move 5V over to where IOREF ended up.
That way existing 5v shields would never
blow up the users DUE because they would be handed IOREF vs 5V.
Those that could work on the lower voltage would
"just work". Those that needed 5v would not work but wouldn't blow up the DUE
and then new shields that really need 5v could get it from the 5V pin.
Overall, I think Microchip has much better solutions as to opposed to an ARM based chip
Solutions that offer much more speed and RAM and resources than Atmel AVR,
and some of the new MIPs based processors are even in DIP packages.
Think of having a PIC based "UNO" type board with a 28 pin dip
that is 32 bit, runs at 40Mhz has 128k flash, 32k of RAM, more internal functions and
no goofy Harvard architecture (progmem) to worry about.
With a processor that that can easily be used for standalone hobbyist designs
all for about the same prices as an Atmel M328.
To me that would have been much more of a winner than the DUE since
it allows the creation of what would be a better "arduino" for essentially the same price.