Are there any other riscv extensions supported on the unmatched board?

HiFive Unmatched
1

Hi,

I have tried to find out this information elsewhere but not been able to find an authoritative source. I can see the unmatched FU740 core supports riscv extensions RV64IMAFDC. But are there any other extensions supported such as Zicsr (Which I assume is present since CSRs work), Zifencei or Zihintpause etc. And if there are some that are supported, is there a list somewhere? And a list for the S7 core?

Thank-you!

2

It is rv64gc which expands to rv64imafdc_zicsr_zifencei. There are no other extensions. The core design is about 3 years old now, so it predates all of the recent ISA extensions. It also predates the change that removed zicsr and zifencei from the I extension.

You can find docs for the SoC at
https://www.sifive.com/boards/hifive-unmatched
Section 1.1 shows that the U74 cores are rv64gc and the S7 core is rv64imac. Since this predates the I/zicsr/zifencei change, the S7 core does include both zicsr and zifencei even though it doesn’t mention them here. Though section 3 which documents the S7 core does mention the fence.i instruction is supported, and mentions various csrs like the pmp registers, so clearly it has both zicsr and zifencei.

3

I see, thanks so much!