HiFive1 Rev B: Custom Risc-V Instructions

I acquired the HiFive1 Rev B Development Kit and I wanted to add custom Instructions.
I searched for related topics but I wanted to ask If it is possible to do this using SiFive tool (freedom Studio), and how whould be the process.

HiFive1 is an ASIC CPU core not a FPGA soft core or emulation. It would be unlikely that it’s reconfigurable enough to add instructions. The most you could do is catch the illegal instruction trap then handle them.

Hi Belen,

The HiFive1 Rev B doesn’t support the SiFive Custom Instruction Extension (SCIE). In fact none of our hardware platforms support it. SCIE is a feature that is tightly integrated into the processor core. When it is enabled, the custom instructions need to be defined at design time. So even if HiFive1 did support SCIE, you wouldn’t be able to add your own custom instructions. You would only be able to use the new instructions that were already designed in.

We have a white paper on SCIE that you might find interesting in our Support Portal: