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Re: Improved memory detection for cgsix


On Wed, 2 Mar 2022 14:49:31 -0500 (EST)
Mouse <mouse%Rodents-Montreal.ORG@localhost> wrote:

> > Looking at the 'Sun GX FBC Reference Manual 3.0' right now.  It's
> > from 1988 though.  It claims [...]  
> > According to the manual mentioned above the framebuffer's stride is
> > selected by two bits in a config register, and can only be 1024,
> > 1152, 1280 or 1600.  
> Yes, I have a PDF which says similar things.  Newer cards have stuff in
> some space that the manual I have documents as unused, which I think
> includes things like more detailed stride control.

That would be nice.
Then again, fb stride doesn't have to match the video output's width,
it just needs to be equal or bigger. Lots of newer chips have weirdo
alignment requirements for their fb strides.

> In particular, I have some relatively-recent cg6s which include
> _built-in_ X resolutions other than those you list.  I have an FCode
> dump that self-identifies as being from a 501-1672 which includes an
> r1920x1080x72 resolution-setting word, in addition to others including
> all four of the X resolutions you list.

Yeah, that would be impossible unless they added something.

> So at least _some_ cg6s can do at least _some_ other resolutions.  How
> much help that is is questionable; if the hardware you have doesn't
> have the capability, knowing how it works on other hardware won't be
> much help.  (I'd also point out that replacing the FCode ROM won't
> somehow render hardware capable of doing things it couldn't before.  I
> don't know if there are cg6s whose hardware can do other resolutions
> but whose FCode can't, though it strikes me as moderately unlikely.)

The video output is more or less programmable, even according to the
manual from 1988. It doesn't say anything about fb stride vs. video
output either though, and clock programming is completely left out.
Older boards have a few oscillators, newer ones have just one, so I
assume those have a programmable clock generator while the older ones
just have bits to select one.

The one I have here tops out at r1600x1280x76 and doesn't list anything
other than the widths mentioned above.

Guess I'll just blit a couple rectangles into VRAM above 2MB and see if
we wrap around or hit the void.

have fun

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