>>>>> "David" == David Hinds <dhinds@valinux.com> writes:
David> No. Read what I said and think about it. My argument is that
David> if you compare a network card that has PCI shared memory, with
David> a network card that does bus mastering to buffers in host RAM,
David> you'll see that exactly the same number of system bus and PCI
David> bus transactions are required to send or receive a packet. In
David> one case the CPU is initiator; in the other the card is
David> initiator. So there is a difference in CPU utilization. There
David> is not a difference in bus utilization. Bus mastering is
David> "faster" because it offloads work from the CPU. PCI bus
David> mastering transactions are not more efficient at the bus level
David> than shared memory transactions: the PCI bus does not
David> distinguish between them, they are all just PCI reads or
David> writes.
They are often very different because you get the streaming effect
when doing bus mastering DMA which you do not get when doing
individual read/writes. Yes there is a big difference.
Jes
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