Re: SS20 cg14 help

[Michael <macallan%netbsd.org@localhost>]

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Hello,

On Aug 4, 2009, at 4:57 PM, der Mouse wrote:

> > > Not quite as nice as it would be if we knew, for example, how to use
> > > the blitter, but still substantially faster than 24bpp by itself.
> > The 'blitter' is actually half of a SIMD CPU nailed to the mainboard
> > - 'half' as in 'no jumps, branches and related stuff'.
>
> I'd heard it said it was a DMA engine - which of course is not very
> inconsistent with what you wrote.

Well, in a way it is. An extremely weird one though.

> I've also seen it said it has access to all of host RAM, not just
> framebuffer RAM, and that this is why it shouldn't be accessible to
> userland in general.

It can access four memory areas which can be anywhere, framebuffer or  
not.

> > You're supposed to feed it instructions through an IO port, it has a
> > bunch of registers, it could probably be used to do stuff like alpha
> > blending but we have no docs at all on the actual instruction set.
>
> Yeah. :(  Like the cg6.

No, it's not anything lik the cg6. The cg6 has registers to feed it  
coordinates and whatnot, the SX works like a CPU - you feed it actual  
SIMD-ish opcodes, not drawing primitives. That's why we don't really  
have a chance to figure it out.

>  (I know how to use the cg6 for things like lines and polygons and  
> rectangular blits, but I understand there's a lot more in there,  
> including full 3D perspective transform....)

The drawing engine is pretty straight forward, the transform engine is  
actually some sort of matrix multiplier which you can use for pretty  
much anything you want, not just coordinate transformation. Well, we  
could if we had actual docs.

> > > I'm a little surprised at the implication that nobody has already
> > > done a both-depths-on-the-screen-at-once cg14 layer for recent X;
> > I guess nobody cares enough.
>
> Sounds that way.  Oh well, it works for me, and if anyone does decide
> to do it, the offer of my code as a starting point is still open. :)

I still hope SX docs will some day materialize on my doorstep, until  
then I'm going to use an AG-10e instead ( and in Solaris at least it's  
actually faster than the SX but if it can do xrender ops things will  
look different )

have fun
Michael

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