Roland> BTW, for "INTx emulation" on PCI Express, there are no
Roland> physical interrupt lines -- interrupts are asserted and
Roland> deasserted with messages. So PCI Express interrupts are
Roland> unshared.
Michael> They are messages upstream that any device.
^ sent
Sorry. Insert "sent" above.
That doesn't parse for me. Was what I said wrong?
No. Just clarifying that they are not unique per device. INTx being a message does not change the fundamental semantics of a "wire" being asserted. Hence, if the wire was shared before, then there is no reason why this would not be the same with PCIe sans. It really is an OS issue as to how INTx interrupts are assigned to different processors and to what extent then end up being shared. The host bridge can play some tricks as well as you noted. Again, the goal within the PCI-SIG is to move people to MSI-X and to eliminate INTx long-term. In fact, one area under development is asking the SIG's members whether INTx can be eliminated entirely which would go a long ways to simplifying designs both in hardware and software.
Mike
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