RISC-V Specifications Platform Software Overview Supervisor Binary Interface 21.1. Experimental SBI Extension Space (EIDs #0x08000000 - #0x08FFFFFF) 21.1. Experimental SBI Extension Space (EIDs #0x08000000 - #0x08FFFFFF) The SBI specification doesn’t define any rules for the EID management for experimental SBI extensions. Chapter 20. Message Proxy Extension (EID #0x4D505859 “MPXY”) Chapter 22. Vendor Specific Extension Space (EIDs #0x09000000 - #0x09FFFFFF)