Re: NetBSD 5.0 and SPARCstation 5 not a lucky combination

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

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Hello,

On Jul 28, 2009, at 1:01 AM, der Mouse wrote:

> > I dimly remember that the old rcons code draws at least the cursor
> > and maybe all text by software and uses the blitter only for
> > scrolling and rectangle fills.
>
> Depends.  Looking at the 3.1 code, I see CG6_BLIT_CURSOR, which if
> turned on seems to do the cursor with the blitter.

I added that option years ago when I found out that it locked up one  
of my CG6. For some reason the same code works fine with wscons.

> As I recall, most of the usability gain from cg6 acceleration came  
> from
> scrolling.  There is some font-draw support in the hardware, but I
> suspect it's not that much faster than software font-draw.

It's several orders of magnitude faster ( I implemented it for  
NetBSD's own xf86-video-suncg6, it beats the pants off most  
contemporary and many newer chips. x11perf -ftext yields more than  
400000 characters per second on a TGX )
But as you said, scrolling is by far the most noticeable acceleration  
feature in the kernel driver.
When using the blitter for all operations we can queue up character  
drawing too instead of having to wait for the blitter to finish which  
is the main reason why I added it to most of my drivers. Less CPU time  
spent spinning.

> > > > Perhaps the next step is shutting [RASTERCONSOLE] off, and seeing
> > > > if the problem persists.
> > > That would be an interesting datapoint.  With no wscons and no
> > > REASTERCONSOLE, console display _should_ go through the PROM
> > > callbacks, AIUI; [...]
> > I'm pretty sure the PROM drawing routines for the cg6 use the blitter
> > for at least a few things.
>
> Yes.  Scrolls, at the very least; it scrolls too fast to be anything  
> else.

Exactly what I thought - see a cg14 for comparison, then add sbus's  
lower bandwidth...

> However, don't callouts to the ROM code run with a bunch of stuff  
> disabled?  That should help some....

I think we disable at least interrupts when calling the PROM.

have fun
Michael

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