RE: DMA across PCI

[Austin Franklin <austin@darkroom.com>]

> I am guessing that there is no such thing as DMA in the PCI world. Is
> that the case ?

Yes there is.  Master is different from DMA.  A PCI 'master' is the device 
that is 'initiating' the transaction on the PCI bus, and it doesn't have to 
be a DMA, it can be a CPU for that matter.  A DMA is what is known as a 
'third party' device, it basically initiates a 'read' from one 'party', and 
then a 'write' to the second 'party'.  It may or may not store the data 
intermediately, it depends on the architecture of the DMA.

The big difference between ISA DMA and PCI DMA is ISA had general purpose 
DMA channels, and PCI DMA is specific to a particular PCI device.

I'd suggest checking out the PLX spec to get a better understanding of DMA 
on the PCI bus.