Dieter wrote:
In message <[email protected]>, James Richard Tyrer writes:
The VGA-to-Ethernet-X11 card could include an X11 client similar to
xterm(1). This might end up being a lot of code to put into firmware
but it should be possible. Anyone disagree? The card's VGA BIOS
routines would have to translate VGA BIOS calls into X11.
Although I did not consider this, it does look like a good idea.
However, the PC spec limits the video BIOS to 64 KiB of system RAM
address space. So, you couldn't have a lot of code.
So, this might mean another MCU would be required to run the actual X
client code.
Ouch! 64 KiB isn't much (kids today probably can't write hello world in
64K). Any workarounds for this? I'd hate to have to add a MCU just because
of a 64 KiB limitation.
The workaround is paging, e.g. having the bios to occupy 64 KB area (or
rather less, to not occupy much of the reserved space and to avoid
conflicts). Then you halve the area - having one static part to which
the interrupt handler refers and one dynamic one, which is switched on
request.
This is the method of overcoming code/data size in microcontrollers with
16-bit address bus. The most difficult part is on the compiler, to
correctly insert page switching..
Daniel
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