[rescue] SBusFPGA update: USB Host, 256 MiB DDR3 RAM disk, ... (Was: Re: A SBus card for SPARCstation designed in 2020...)

[Romain Dolbeau]

Le jeu. 21 oct. 2021 C  01:08, Mouse <mouse at rodents-montreal.org> a C)crit :
> Yeah, the cg6 has registers for Z coordinates but they don't seem to do
> anything.  I don't know whether 3D was planned but never implemented or
> whether it's just that how to get it to do anything but parallel
> projection down the Z axis is not publicly known.

Documentation on the GX architecture has recently surfaced at bitsavers:
<http://bitsavers.org/components/lsiLogic/sparc/GX/>
>From the FBC (Frame Buffer Controller) doc:
"The Z registers do not store a Z value, but are used when the Z clip
information is autoloaded from the TEC."

The TEC is the Transformation Engine & Cursor.

> The extra bits
> specify whether the other 24 bits are sent straight to the DAC
> (TrueColor, in X terms), sent through lookup tables to the DAC
> (DirectColor), or whether the green channel is sent to all three lookup
> tables and thence to the DAC (PseudoColor)

That should be reasonably easy to do, it just takes some FPGA
resources and perhaps some extra cycles for all the look-ups
(pipelined so won't matter).

> Depends on how you define `mature', but actually probably not.

"mature" has in "has been used so long with limited functional changes
so that most of the bugs have been sorted out".

> Personally, I would pay a small amount extra to _not_ have HDMI, quite
> aside from what other connector(s) it has/have.  (But I probably am an
> extreme outlier in that respect.)

I'm assuming you have an issue with licensing or something like that?
When I say 'HDMI' in this context, it just means 'an HDMI connector
with signals that an HDMI monitor will understand'.
No HDCP and probably missing a bunch of features from 'true' HDMI.
Basically a digital version of VGA :-)
Though you'd still need a HDMI monitor...

Cordially,

--
Romain Dolbeau