In a previous episode, Fernando D. Mato Mira claimed:
> At 05:15 PM 10/18/98 -0700, you wrote:
> > XZ is one of the variants of the Elan/Extreme series of cards,
> >which have one or more geometry engines on the card. The geometry
> >engines need microcode downloaded for full functionality, and the
> >interfaces are not externally documented, so it is hard to build
> >linux support without access to the IRIX source for reference.
>
> What about just getting the console running (no X server)?
> How do GR2 (Indigo Elan) and GR3 (Indigo II Elan) differ in terms of
> programming?
>
I did some asking around. Here's what I found:
* In order to do anything, you have to download microcode.
* The monitor PROM downloads a mini-microcode that could be used. I am
not sure what the entry points look like to the PROM. I think this
is the safest bet.
* The full-functioning microcode (that does 3d) is downloaded at boot
time before the X server initializes.
* The people that I asked are not clear about the programming differences
between GR2 and GR3. Certainly they are the same for OpenGL-level
programming. My guess is that there are differences in the CPU interfacing
and video back end. User-level code is the same, but kernel initialization
and management code may be different.
* Getting things up and running on a GR-type (Express) architecture is
definetely more difficult than Newport.
* Documentation will be hard to find. Documentation for programming the
microcoded engines, even harder. You could, of course, use the existing
microcode.
--george
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