[J-core] How crazy would a nommu debian port be?

Rob Landley rob at landley.net
Tue Aug 23 17:54:52 EDT 2016

On 08/23/2016 03:39 PM, Rich Felker wrote:
> On Tue, Aug 23, 2016 at 11:50:58AM -0700, Cedric BAIL wrote:
>> pixman and cairo is a lot of work and quite invasive too. The
>> Raspberry Pi had this 2D unit for years, it never took off and they
>> have a very large user base with a constrained hardware. Arguably
>> people may have settled for their OpenGL core as it require less work
>> to get that one going. Still, I think maintaining a custom 2D engine
>> in any libraries is going to be a hard task.
> Outside of the J-Core project, efficient 2D UI rendering, including
> modern (multilingual, high-res, antialiased) text rendering, with very
> small code and hardware requirements, is a major interest of mine, but
> I don't know if/when I'll get a chance to work on it.

I just checked and that xterm you wrote way back when still isn't up on
https://github.com/richfelker :)

>> A simple support for a fixed number of hardware plane with various
>> color space support, clipping and color multiplier could be exposed as
>> a kms/drm/dmabuf output and would require no change in userspace to
>> leverage it.
> Oh yeah, maybe the kernem dmabuf stuff already allows software to take
> advantage of dma copies/fills.

One advantage of the hardware being open source is if somebody _wants_
to do commodore-64 style sprites (with collision detection and
everything) and use them to implement their own pac man game, nothing's
stopping them. :)

>> Do you think there will be enough space on the Turtle to actually have
>> SMP, HDMI, ethernet and both DMA as described in this email ?
> Yes.

I believe Turtle FPGA's over twice as many cells as Numato Mimas v2 and
twice the DRAM. Plus a lot more builtin I/O connectors. We're trying to
keep it under twice the price of the Numato.

> I'm not sure if the final Turtle will use an LX25 or LX45,

Current prototypes are LX25, LX45 adds too much to the cost. :(

> but given that everything in the current release fits in an LX9, even if
> it were using the whole LX9 and even if SMP doubled the FPGA space
> needed, there'd still be almost 1/3 of an LX25 (about the space of a
> whole LX9) free for HDMI, ethernet, DMA, USB, etc. The prototype I
> have with LX25 has SMP and ethernet already.

LX25 is 25k cells vs LX9 at 9k cells, so not quite 3x. But current J2
designs don't completely fill up an LX9 either, and there's some sharing
with SMP (only one DRAM controller, etc).

I'm sure Geoff has actual numbers. :)

> Rich


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