Wiring up a whole bunch of AVR MCUs is useful if I want to control a lot of I/O pins very quickly (motor control), but for my deep learning and machine vision it would be cheaper and a more efficient use of space if I just get an SBC or even use a GPU. Also, programming the necessary number of small MCUs to do this is incredibly tedious and difficult to manage. I do think it is a good idea though the next time I need to write to a huge amount of I/O pins. The ATmega328P only has 16 DMIPS of processing power, whereas a Raspberry Pi 2 has nearly 7000 DMIPS! It would take a great many AVR chips to match that kind of processing power, plus it would require much more power due to so many separate chips. An alternative is for me to create a smaller cluster of much more powerful processors, such as a group of low-power ARM Cortex-A Series chips for the machine learning and vision and AVRs or ARM Cortex M Series processors for motor and basic I/O control (including gyroscopes, accelerometers, force sensors, you name it).