from Hacker News

ULX3S: Hackable FPGA that runs Linux on RISC-V

by herogreen on 6/13/20, 9:59 PM with 79 comments

• by herogreen on 6/13/20, 10:12 PM

  Also newsworthy: Lattice drops recent EULA clause forbidding fpga bitstream reverse engineering https://hackaday.com/2020/06/06/lattice-drops-eula-clause-fo... therefore 2020 could be a milestone for open FPGA toolchains!

• by haberman on 6/14/20, 12:28 AM

  Is there any published rationale for the RISC-V instruction encoding?

  A few months back I set out to write a software emulator of RISC-V for fun. I expected the instruction set encoding to lend itself well to a very simple implementation, eg. something you could decode in 5-10 lines of C plus some tables.

  But the instruction encoding is much more irregular than I expected: https://github.com/ucb-bar/riscv-sodor/blob/master/src/commo...

  In particular:

      - The bit patterns allocated to the simplest instructions
        (eg. rv32i) seem random. Why not allocate starting from zero
        to allow dense jump tables?
      - I can't make any sense of the groupings. A bunch of instructions
        have 0b1100011 in the lowest bits, do these instructions have
        something in common?
  

  I assume there is some rhyme and reason to all this? Where is this explained?

• by q3k on 6/13/20, 10:37 PM

  The ULX3S is great! I built myself an early prototype a year ago, and have used it every so often for occasional hacks. It has since evolved to be a first-class citizen in a number of projects and frameworks (LiteX, including LiteDRAM), which makes it great to get started with.

  Also worth noting, that you can use a fully open source flow (Yoys + nextpnr + prjtrellis) for this FPGA family. Here's a repository I made that shows a basic blinky for an ULX3S: https://github.com/q3k/ulx3s-foss-blinky/

• by tyingq on 6/13/20, 11:35 PM

  Where's the article? I see mostly a bunch of loosely related bullet points.

  Edit: After a lot of back and forth, perhaps this is a good intro: https://hackaday.com/2019/01/14/ulx3s-an-open-source-lattice...

• by bloopernova on 6/13/20, 11:03 PM

  Layman question: how many years before we get RISC-V desktops or Raspberry Pi like computers?

• by ngcc_hk on 6/14/20, 12:20 AM

  Remember there is a lecture by a guy who demo on a game emulation program. Wait for it since.

  Just placed an order : https://www.crowdsupply.com/radiona/ulx3s

• by wolrah on 6/14/20, 2:48 AM

  Can anyone comment on how this compares to the popular Terasic DE10-Nano used for the MiSTer project? The price point is around the same and I see they note running video game cores as a market for this device, but I have absolutely no clue how to reasonably compare FPGAs.

  From my rudimentary understanding it looks like this doesn't have a hard CPU and has a smaller FPGA, so I'm guessing we have a fair bit of "open hardware tax" at play here too.

• by pjmlp on 6/14/20, 7:06 AM

  Cool! It also does Oberon, MicroPython and Basic.

• by b1ackb0x on 6/14/20, 5:44 AM

  Is it any better than Artix-7 XC7A100T or XC7A35T boards from Aliexpress(search QMTECH, they sell 100K board for ~$100)?

• by sitzkrieg on 6/13/20, 11:19 PM

  very impressive project, its a good time to get into fpga projects

• by gre on 6/14/20, 12:34 AM

  How does it compare to the Arty A7 for $129?

• by lihaciudaniel on 6/14/20, 3:31 PM

  Theoretically every fpga is hackable

• by johan_larson on 6/13/20, 11:37 PM

  The dollar sign comes before the number, not after it.

  $150

• by rasz on 6/13/20, 11:04 PM

  2x more resources compared to $30 https://github.com/q3k/chubby75 at 5x the price