Re: IRQ 255?
aem@netcom.ca
Thu, 29 Jan 1998 00:54:46 -0500 (EST)
> > Does anyone know what the advantages/disadvantages of having an irq for a video
> > card are?
>
> In general: No advantage. Most of the time, the video card justs listens
> to what is written into its framebuffer and displays it. More advanced
> cards do accept simple commands that they can perform itself. (Draw lines,
> fill polygons, etc.) Very advanced cards do fullfill complicated tasks and
> signal that they are ready and wait for new tasks/data by an interrupt. 3D
> chips can be considered as very advanced.
AFAIK the IRQ is only used for scan events. Seems most software polls
for these though.
XFree86 does not use any IRQ handlers that I know of. The Matrox
server definitely doesn't.
IRQs are also used by video add-on cards (capture, TV, MPEG)
--
Andrew E. Mileski mailto:aem@netcom.ca
XFree86 Matrox Team Member