[Arm-netbook] libre 64-bit risc-v SoC

mike.valk at gmail.com mike.valk at gmail.com
Fri Apr 28 11:35:19 BST 2017

2017-04-27 13:21 GMT+02:00 Luke Kenneth Casson Leighton <lkcl at lkcl.net>:

> ok so it would seem that the huge amount of work going into RISC-V
> means that it's on track to becoming a steamroller that will squash
> proprietary SoCs, so i'm quite happy to make sure that it's
> not-so-subtly nudged in the right direction.
> i've started a page where i am keeping notes:
> http://rhombus-tech.net/riscv/libre_riscv/ and the general goal is to
> create a desirable mass-volume low-cost SoC, meaning that it will need
> to at least do 1080p60 video decode and have 3D graphics capability.
> oh... and be entirely libre.
> the plan is:
> * to create an absolute basic SoC, starting from lowRISC (64-bit),
> ORGFX (3D graphics) and MIAOW (OpenCL engine), in at least 90nm as a
> low-cost proof-of-concept where mistakes can be iterated through
> * provide the end-result to software developers so that they can have
> actual real silicon to work with
> * begin a first crowd-funding phase to create a 28nm (or better)
> multi-core SMP SoC
> for this first phase the interfaces that i've tracked down so far are
> almost entirely from opencores.org, meaning that there really should
> be absolutely no need to license any costly hard macros.  that
> *includes* a DDR3 controller (but does not include a DDR3 PHY, which
> will need to be designed):
> * DDR3 controller (not including PHY)
> * lowRISC contains "minion cores" so can be soft-programmed to do any GPIO
> * boot and debug through ZipCPU's UART (use an existing EC's on-board

Perhaps put it sirectly to an USB bridge. UART's on debugging hardware is
non existant. We all use FTDI dongles.

Look like OpenCores has a module. https://opencores.org/project,usb2uart

> * OpenCores VGA controller (actually it's an LCD RGB/TTL controller)
> * OpenCores ULPI USB 2.0 controller
> * OpenCores USB-OTG 1.1 PHY
> note that there are NO ANALOG INTERFACES in that.  this is *really*
> important to avoid, because mixed analog and digital is incredibly
> hard to get right.  also note that things like HDMI, SATA, and even
> ethernet are quite deliberately NOT on the list.  Ethernet RMII (which
> is digital) could be implemented in software using a minion core.  the
> advantage of using the opencores VGA (actually LCD) controller is: i
> already have the full source for a *complete* linux driver.
> I2C, SPI, SD/MMC, UART, EINT and GPIO - all of these can be
> software-programmed as bit-banging in the minion cores.
> these interfaces, amazingly, are enough to do an SoC that, if put into
> 40nm, would easily compete with some of TI's offerings, as well as the
> Allwinner R8 (aka A13).
> i've also managed to get alliance and coriolis2 compiled on
> debian/testing (took a while) so it *might* not be necessary even to
> pay for the ASIC design tooling (the cost of which is insane).
> coriolis2 includes a reasonable auto-router.  i still have yet to go
> through the tutorials to see how it works.  for design rules: 90nm
> design rules (stacks etc.) are actually publicly available, which
> would potentially mean that a clock rate of at least 300mhz would be
> achievable: interestingly 800mhz DDR3 RAM from 2012 used 90nm
> geometry.  65 down to 40nm would be much more preferable but may be
> hard to get.
> graphics: i'm going through the list of people who have done GPUs (or
> parts of one).  MIAOW, Nyuzi, ORGFX.  the gplgpu isn't gpl. it's been
> modified to "the text of the GPL license plus an additional clause
> which is that if you want to use this for commercial purposes then...
> you can't". which is *NOT* a GPL license, it's a proprietary
> commercial license!
> MIAOW is just an OpenCL engine but a stonking good one that's
> compatible with AMD's software.  nyuzi is an experimental GPU where i
> hope its developer believes in its potential.  ORGFX i am currently
> evaluating but it looks pretty damn good, and i think it is slightly
> underestimated.  i could really use some help evaluating it properly.
> my feeling is that a combination of MIAOW to handle shading and ORGFX
> for the rendering would be a really powerful combination.
> so.
> it's basically doable.  comments and ideas welcome, please do edit the
> page to keep track of notes http://rhombus-tech.net/riscv/libre_riscv/
> ---
> crowd-funded eco-conscious hardware: https://www.crowdsupply.com/eoma68
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