My name is Yunhao and I am an instructor at Cornell teaching operating systems. We are trying to port our educational OS and course projects onto HiFive, so that our future students can enjoy playing with the board while studying OS.
The key obstacle we met is that HiFive doesn’t seem to have enough memory. It seems to have 32KB memory in total, which is too few for running our OS. Ideally, we wish to have a few megabytes of memory (say 4MB).
One way we can get around is to use the Arty FPGA board instead of HiFive and Arty has 256MB of DDR3 memory. But this doesn’t sound like a graceful way.
Please let me know if there are any ways that I can get a relatively cheap board like HiFive, while get some additional memory, say 4MB. If this is possible and we complete our work on porting the OS, our future students will largely benefit from HiFive which would be great!
The Kendryte K210 SoC has dual 400 MHz 64 bit RISC-V CPUs and 8 MB of SRAM. Plus a lot more stuff. Basic boards start from $13, an Arduino-like board is $21, and a board in a case with LCD touch screen is $39. (I have one of each)
So I spend another winter for this project and eventually solve the problem by
use the Arty FPGA board and run the SiFive FE310 processor
modify the processor and increase the memory to 160KB (from 32KB), which is the limit of Arty
connect the FE310 SPI1 to the Pmod1 ports of Arty and plugin a microSD Pmod to the board
use SPI1 to control the microSD card for memory swapping
Now the hardware is suitable to run our teaching OS at Cornell and I plan to finish it this spring. Ideally, we can use the SiFive processor and the Arty board to teach OS this fall.