Curious why using mmap IO I can only toggle a GPIO pin (P8_12) at 2.78MHz. 
It seemed fast to me but my coworkers are laughing and saying its pathetic 
;)

My code: https://dl.dropboxusercontent.com/u/82765462/BBB/gpio.c

Borrowed from Mark Yoder's 
example: http://elinux.org/EBC_Exercise_11b_gpio_via_mmap

Same result as this person: http://chiragnagpal.com/examples.html

Compile:

gcc -o gpio gpio.c 

Then run:
echo 44 > /sys/class/gpio/export
echo "low"  > /sys/class/gpio/gpio44/direction

Then 
./gpio

And measure on a scope...

Screenshot: https://dl.dropboxusercontent.com/u/82765462/BBB/gpio_mmap.jpg

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