The ZipCPU and several peripherals can fit within an iCE40 8k using only about 5k LUTs--and that's with the multiply unit, the divide unit, the pipelined fetch

The ZipCPU and several peripherals can fit within an iCE40 8k using only about 5k LUTs--and that's with the multiply unit, the divide unit, the pipelined fetch unit, and a debugging bus infrastructure. While that isn't the full pipelined implementation neither do the caches fit, it is sufficient to be competitive with the picoRV.