Re: IRQ 255?
Brian Gerst (bgerst@quark.vpplus.com)
Wed, 28 Jan 1998 21:18:21 -0500
Kurt Garloff wrote:
>
> On Thu, 29 Jan 1998, Ian Eure wrote:
>
> > 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.
> I have no idea, if some of the accelerated XFree86 servers make use of
> interrupts, but I guess so. The Glide library and maybe also the MesaGL
> (OpenGL clone) could profit, too. But as Unix software tends to be
> portable and interrupts aren't, I'm not sure.
XFree86 cannot use the interrupts, because it is a user-space program.
Interrupts are only available within the kernel. GGI however can use
the interrupts, since the KGI part of it puts low-level video drivers
into the kernel.
--
Brian Gerst