Graphics in embedded systems?

[Gabriel Paubert]

On Wed, 14 Feb 2001, Patrik Olesen wrote:

>
> What do I need to run graphics on a MBX860 card?
>
> Is it possible to use a standard VGA card connected to PCI and then run
> Xlib?

Blatant plug: one of the problems may be to initialize the board. I have
an x86 ROM BIOS emulator which does the job quite nicely on my S3 boards.
It's even embedded in a bootloader (prepboot) and rather small for an
emulator (approx 24k).

Once the board has been correctly setup, standard libs should work

> If so, what requirements has such a configuration regarding RAM, ROM and CPU...

You need a way to access ISA VGA addresses (0xa0000-0xbffff), and ISA I/O
addresses for VGA. Beware of conflicts, especially with S3, which uses a
bunch of I/O addresses of the form 0x2e8+n*0x400 (inherited from IBM's
8514 AFAICT). My solution is that the PCI devices are allocated I/O
addresses starting from 0x10000. The ROM only has to be virtually located
at 0xc0000 for it to work. I copy ROM to RAM to accelerate the emulator
and then play with memory management to build a PC low 1Mb memory map.

The ROM BIOS on my machine uses standard PC ports 0x42-43 and 0x61 for
timing purposes. I don't have any problem since these devices exist on
PreP machines, but if you don't have them, you'll have to emulate the
8253.

	Gabriel.


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