Food for thought. Thanks for everyone's input. I personally have not been involved with the Linux software that is running on the Crystalfonz SOM I mentioned previously. I designed the external hardware to connect to the SOM and used the GPIO pins available to create an 8 bit 8080 byte bus, i.e. 8 data bits, 6 address bits, one read bit and one write bit. I designed it for up to 10 Mhz bandwidth. I assumed the software driver would have to bit-bash the read and write control signals but was naive to assume one could read/write the 8 data GPIO pins in one operation. This has not been an issue as yet but I was looking at trying to do it better on any new SOM we try. I have not tried using a Raspbery Pi and do not know much about them from the software development side of things - this is why I asked my original question, albeit the wrong question for what I was looking for. The application(s) I am involved with require low level hardware to access peripherals on an external bus AND high level stuff like 800x480 colour LCD touch screens, Ethernet and USB.
So thanks again. I think I have enough information now to look more closely at any SOM (even the Pi), so I think it would be prudent to close off this discussion at this point.
