RISC-V Specifications Platform Software Overview Supervisor Binary Interface Chapter 23. Vendor Specific Extension Space (EIDs #0x09000000 - #0x09FFFFFF) 23.1. Vendor Specific Extension Space (EIDs #0x09000000 - #0x09FFFFFF) The lower 24 bits of vendor specific EID must match the lower 24 bits of the mvendorid value. Chapter 22. Experimental SBI Extension Space (EIDs #0x08000000 - #0x08FFFFFF) Firmware Specific Extension Space (EIDs #0x0A000000 - #0x0AFFFFFF)