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SubjectRe: alpha iommu fixes
At 10:24 PM +0100 2001-05-22, Alan Cox wrote:
> > On the main board, and not just the old ones. These days it's
>> typically in the chipset's south bridge. "Third-party DMA" is
>> sometimes called "fly-by DMA". The ISA card is a slave, as is memory,
>> and the DMA chip reads from one ands writes to the other.
>
>There is also another mode which will give the Alpha kittens I suspect. A
>few PCI cards do SB emulation by snooping the PCI bus. So the kernel writes
>to the ISA DMA controller which does a pointless ISA transfer and the PCI
>card sniffs the DMA controller setup (as it goes to pci, then when nobody
>claims it on to the isa bridge) then does bus mastering DMA of its own to fake
>the ISA dma

That's sick.
--
/Jonathan Lundell.
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