Graphics Processor and Frame Buffers

[Daniel McCoy]

lecgwy!mdlrth.dnet!coco at rutgers.edu (Joe X3238) writes:
>I have a 3/260 CXP with a GP2 graphics processor.  I don't know much about
>the GP2 and I will need to start using it soon.  There are a few things I
>don't understand :
>
>-  What is the difference between the default frame buffer(/dev/fb) and the
>   cgtwo frame buffer(/dev/cgtwo)?  The documentation says that the GP2 can
>   only be bound to cgtwo frame buffers. Is this the case?  Could I (or would
>   I want to) bind the GP2 to /dev/fb?

You wouldn't want to.  /dev/fb is not a real device, see the man page for
fb(4).

>-  If gpconfig redirects /dev/fb to use GP2, what is the difference
>   between these two window invokations :
>	sunview
>	sunview -d /dev/gpone0a

The second one may have synchronization problems if you run programs under
sunview that open /dev/fb explicitly (bad) rather than finding the device
through the window system (good).

>-  Does the GP2 add any performance to regular window operations such as
>   resizing, moving etc.

Not much. 

>-  Does allowing sunview to run on a frame buffer and not the GP2 give you
>   anything?  e.g. sunview -d /dev/cgtwo0

It gives you synchronization problems if you run programs under sunview
that access /dev/gpone0a.  Also programs that play by the rules and get
the device from the window system won't know you have a GP2.

>-  Any other general information about experiences with programming the
>   GP2 using either GPSI or the Viewport Package would be appreciated. 

Avoid the Viewport Package.  Period.  The DEV_GP1 package is easier to
deal with.  Using GPSI directly is doable, but if you do, plan to spend
some time debugging buffer stuffing code.  DEV_GP1 will save you from the
most of the headaches.

Performance tips:
-For vectors, pack a lot of points into each command.
-Grouping like commands together is faster than mixing them up.
-Eat more vegetables and less fat.

	Dan McCoy