According to the documentation, the E310 uses the RV32IMAC on the Artix-7 FPGA. Has anyone tried to put an RV64I on it instead?
If it was 64 bit then it would be an E51, not an E31.
https://dev.sifive.com/dashboard/deliverables/sifive_e51_fpga_eval_kit_bitstream/releases/v3p0/
Thanks for the answer. Do you know what the limiting factors are for putting an RV64I on an E31? Is it pins? Area? Just curious. 
The limiting factor is that the E31 is what we call our Rocket-based 5 stage pipeline in-order single dispatch core generator when it is configured to produce a core implementing rv32imac.
If we keep everything the same but configure it for rv64imac instead then we call it E51. Which you can download and try on your Arty.
Just to be clear, here is the link to an RV64IMAC core you can download and try on your Arty:
https://dev.sifive.com/dashboard/deliverables/sifive_e51_fpga_eval_kit_bitstream/releases/v3p0/
Hi Bruce, that’s awesome! Thanks for the link!
No problems, and happy experimenting!