On Wed, 4 Jul 2001, Andreas Beck wrote:
> Hi,
>
> > To access Video-RAM there are two ways: One through the Bus and one
> > through a memory-"window", which is stored in physical RAM.
>
> Huh ? How does the card access that ? using Busmaster-DMA ?
Yes.
> In that case it gets very tricky, because, you will need kernel help
> to get the physical address of the window and moreover on 64 bit
> architectures, you need a way to allocate memory in the range that
> is available for Busmaster-DMA.
In other words: This can _never_ be target-independent, right?
So, then access handling to physical RAM must always implemented in
the target.
> > I wanna know, if there is a generic (= target-independet) way to get
> > read/write access to that "window".
>
> Are you absolutely sure that this is what "window" means ?
>
> There is often talk about acess windows that work vice versa, i.e. by
> mapping parts of the VRAM into the physical RAM adress space (the old
> VGA 64k window at 0xa0000 is such a case), but I have rarely heard about
> the other way round, except for unified memory architectures, where
> System RAM == VRAM.
Uhmm... When you buy a new graphic card, aren't you wondered why it
requires a certain amount of system RAM ?
CU,
Christoph Egger
E-Mail: [EMAIL PROTECTED]
