[J-core] Linux on J1?

[Rob Landley]

What would it take to build a J1 processor running Linux?

What I mean by that is, presumably starting with:

  http://lists.j-core.org/pipermail/j-core/2016-June/000204.html

1) Take the stripped down "should fit in ice-40 if the toolchain works"
config and build it for spartan 6 with the existing xilinx toolchain.

2) Add the DRAM controller back.

3) Audit the instruction set and decide what we want to keep/drop. Do we
want a microcoded multiplier, or have libgcc.a do it? We talked about
this a few times:

  http://lists.j-core.org/pipermail/j-core/2016-May/000166.html
  http://lists.j-core.org/pipermail/j-core/2016-May/000169.html
  http://lists.j-core.org/pipermail/j-core/2016-July/000252.html

4) Tweak gcc/binutils to add a target to produce the right instructions.

5) Tweak the kernel assembly.

6) Boot Linux on a Numato board with J1.

Now here's the really funky question: If we just use prefetch instead of
icache/dcache, could we SMP J1 on Numato? (And/or fit in one instance of
the DSP?)

Rob