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

**URL:** <https://forums.sifive.com/t/are-there-any-other-riscv-extensions-supported-on-the-unmatched-board/5664>\
**Category:** HiFive Unmatched\
**Created:** [March 28, 2022, 12:30pm UTC](https://forums.sifive.com/t/are-there-any-other-riscv-extensions-supported-on-the-unmatched-board/5664 "2022-03-28T12:30:01Z")\
**Posts on this page:** 3\
**Page:** 1

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**Author:** ![yuumei](https://avatars.discourse-cdn.com/v4/letter/y/4bbf92/32.png) [@yuumei](https://forums.sifive.com/u/yuumei)\
**Post date:** [March 28, 2022, 12:30pm UTC](https://forums.sifive.com/t/are-there-any-other-riscv-extensions-supported-on-the-unmatched-board/5664/1 "2022-03-28T12:30:01Z")

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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!

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**Author:** ![JimWilson](https://avatars.discourse-cdn.com/v4/letter/j/3be4f8/32.png) [@JimWilson](https://forums.sifive.com/u/JimWilson)\
**Post date:** [March 28, 2022, 2:25pm UTC](https://forums.sifive.com/t/are-there-any-other-riscv-extensions-supported-on-the-unmatched-board/5664/2 "2022-03-28T14:25:09Z")

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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](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.

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**Author:** ![yuumei](https://avatars.discourse-cdn.com/v4/letter/y/4bbf92/32.png) [@yuumei](https://forums.sifive.com/u/yuumei)\
**Post date:** [March 28, 2022, 3:19pm UTC](https://forums.sifive.com/t/are-there-any-other-riscv-extensions-supported-on-the-unmatched-board/5664/3 "2022-03-28T15:19:28Z")

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I see, thanks so much!