The question of this topic is already in the header but I try to describe my intention a little bit:
I read about some projects which use the Allwinner V3s or A13, but no one really uses the F-Series processors, linux-sunxi even say, that they don't support it (
http://linux-sunxi.org/Allwinner_SoC_Family), which is unfortunate.
In my opinion these processors are a great starting point for people who want to get into developing a "System on Chip" - PCB but don't want to deal with high speed interfaces and BGA routing / soldering like one has to with DDR2/DDR3.
For example, the F1C500 (
http://www.allwinnertech.com/index.php?c=product&a=index&id=27) has enough hardware on-board (UART, SPI, I2C), is available for 3$ at aliexpress and probably has more processing power than any other microcontroller (like M7 etc.). It has a SDR-RAM interface, there are plenty of TSSOP SDR-RAM chips out there - so that's nice.
It is also comes in a solderable QFP package.
The only problem I have at the moment: There is only a very short user-manual but no reference-manual (like there is for the V3s) available. So I would like to ask kindly, if anyone here has access to a more detailed description of the processor?
Edit: I know, they are really old chips but still available and not too complex hardware (in my opinion). ARM9 should also support JTAG. I also know, that a closed-source RTOS from Allwinner runs on those chips but I don't think it is available to the public - at least I didn't find anything source-code related.