The SiFive HiFive1 Rev B is a SBC funded on Crowd Supply featuring the Freedom Everywhere FE310-G002 RISC-V processor capable of being clocked at 320+ MHz.
The FE310-G002 jumps to
0x2001_0000 in the external SPI Flash memory on the HiFive1 Rev B. The FE310-G002 can boot from other sources, controlled by the Mode Select (
MSEL[1:0]) pins. The default value appears to be
01, which is a jump to
0x2000_0000 in external SPI Flash. It may also be defaulting to
10, a jump to the OTP (One-Time Programmable) memory at
0x0002_0000, which could then jump to one of the previous locations in external Flash. The other two options are
11 for the fixed mask ROM, which contains an instruction at
0x0001_0000 to jump to the OTP memory, and
00, which jumps to
0x0000_1004 and loops forever waiting for a debugger.