Am I right in thinking 8K refers to the number of LUTs/cells? If so I won't be fitting the Rocket RISC-V design in one any time soon. Although it's a good start - I'll be very happy to see the back of Xilinx Vivado awfulness one day.

PicoRV32 (https://github.com/cliffordwolf/picorv32) and ORCA (https://github.com/VectorBlox/orca) are two RISC-V implementations that nicely fit in ~2000 iCE40 LUTs. UCB-BAR V-Scale (https://github.com/ucb-bar/vscale) fits in ~4000 iCE40 LUTs.

There is a Pico Risc-V that fits in ~2000 LUTs that can be built for the ice40: https://github.com/cliffordwolf/picorv32 https://github.com/cliffordwolf/picorv32/blob/master/scripts...

I stand corrected. See Clifford's other comment in this thread.