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SubjectRe: PCI Bursting with PIO
On Fri, Feb 15, 2008 at 5:02 AM, Alan Cox <alan@lxorguk.ukuu.org.uk> wrote:
> > Is there any way to get PIO to burst over the PCI bus in the read and
> > write direction? My device has 4 BAR registers, but the area where I
>
> I think you are doign about as well as the X folks did when they spent
> time on trying to optimise pio transfers to and from graphics card RAM.
>

That's good to know. Do you have a link or anything to their
discussion or some key words that I could hunt it down?

>
> > Any ideas would be really appreciated,
>
> Put a DMA controller on it ;)

Ugh.. sadly that's what's coming. I really don't get why the
northbridge cannot burst however. If the memory is mapped
prefetchable and you have to do a PCI read through 3 PCIe bridges to
finally get to your device it seems like it would _really_ behoove the
bridge to do a Memory read multiple and get the whole cache line. I
have searched around a lot and there doesn't seem to be any info at
all on how you can persuade these bridges to do different PCI commands
or burst. I don't know why....

thanks again for your help,

dan


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