[rescue] EIO card in HP 4M

[Romain Dolbeau]

Le mar. 13 avr. 2021 C  13:09, Mouse <mouse at rodents-montreal.org> a C)crit :
> > Given the amount of people recreating PCBs for old hardware
> > (OpenTendo, SnarkBarker, replacement motherboards), I wonder what it
> > would take to make replacement VSIMMS.
> In a word, I would guess, documentation.

Indeed. The cg6 was well documented but the others, not so much.

Having played with FPGA in my SS20 (i.e.
<https://github.com/rdolbeau/SBusFPGA>), an alternative solution would
be to recreate a framebuffer from scratch.
Even entry-level FPGA such as the Artix-7 can do a decent framebuffer
- I tried a non-accelerated one at 1024x768 at 75 Hz outputing to a
modern HDMI connector as part of a LiteX SoC
(<https://github.com/enjoy-digital/litex>) and that works fine in
Linux (Artix-7 100T-2 on a ~$90 chinese board). Extra benefits would
be compatibility with newer interfaces/screens.

With a proper PCB design (an expertise I unfortunately do not have,
mine is much simpler as the FPGA is on a commercial board, which is
why I don't have a HDMI connector), it should be quite possible to
design a SBus-based framebuffer, including compatibility with a CG3 or
TCX (there's already some reimplementations in e.g.
<http://temlib.org/>).

Unfortunately, SBus connectors are EOL'ed so it's going to be much
more difficult in the future.

Cordially,

--
Romain Dolbeau