Re: CG14 in 8-bit color

[Romain Dolbeau <romain%dolbeau.org@localhost>]

Le ven. 3 déc. 2021 à 18:25, Michael <macallan%netbsd.org@localhost> a écrit :
> As promised I finally sat down to make suncg14 work in 8bit.

Oh nice :-) Though as the only SPARCstation 24-bits display that isn't
entirely mythical, it seems weird to use it in 8-bits.
Even for the higher resolution as Malte does...

Annoyingly, I couldn't get my pseudo-cg6 in the SBusFPGA to do
1920x1200, it seems the 193+MHz pixel clock is too high (a faster FPGA
would definitely work though). The 148.5MHz of 1920x1080 is fine now.
(except I still can't for the life of me figure out why my version of
the cg3 or cg6 causes X11 to corrupt UVM, when I don't change the
software at all).

> That's a weirdness in SX's STBS ( STore Bytes from Scalar )
> instruction, if you store a bunch of bytes from a scalar you need to
> repeat the byte-to-be-stored in all four sub-bytes of the source
> register. Apparently that saved the designers a few gates on the chip,

Well that's less routing of data from the LSB to the others (and
associated control), so it figures out it would be cheaper in silicon.
Is there some easy way to broadcast a byte to all the bytes in the
(vector) registers, or does it have to be handled by the host?

They probably didn't expect much accelerated use in 8-bits -
presumably the primary design point was 8-bits console with
accelerated scrolling and 24-bits X11 with full acceleration.

> I fixed a handful pixels-are-32bit (...)

By the way, thank you so much for doing all that work for
NetBSD/sparc, it is very much appreciated!

Cordially,

-- 
Romain Dolbeau