– Why did you select an altera FPGA (EP4CE15E22) and why not another one from Xilinx for example? Are there any good reasons?
There was a couple reasons behind I ended up with EP4CE15E22:
* FPGA had to be relatively cheap and hand-solderable (no BGAs)
* During early development I used DE2-115 development board which had higher-end Cyclone IV FPGA, so it was easy transition to EP4CE15E22
* My short experience with Xilinx’s tools (ISE) wasn’t very positive, although I have to say they didn’t suck nearly as badly as many ASIC design tools. While Quartus is not perfect either, it has worked better for me
* Xilinx’s FPGAs seemed to be more geared towards professional design instead of hobbyist prototyping (availability, pricing etc.). Take a look e.g. how many Xilinx FPGAs Mouser offers versus Altera
Where is saved the bitstream?
It’s saved on a serial flash IC, which FPGA automatically reads at power-on
Do you use any soft core in OSSC?
Yes, it uses basic (free) version of Nios 2. If I had more time on my hands, I’d rather put LM32 or RISC-V running on the FPGA