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    SubjectRe: Safety of IRQ during i/o
    On 25 Jul 2002, Alan Cox wrote:

    > There are also some older systems where if the block transfer of the IDE
    > data didn't keep up with the controller instead of handshaking properly
    > it kind of dribbled random numbers onto the disk.
    > Unless anyone knows of PCI era devices with this problem I would be
    > inclined to agree that we should default to IRQ unmasking in the 2.5 IDE
    > code if the IDE controller is PCI.

    Certainly if the controller is running in DMA mode. If running in PIO mode
    I would think you could still have a problem if the transfer was stopped
    mid-block. Perhaps I'm paranoid, is that a "can't happen" now?

    > For old ISA/VLB controllers its safer left as is, and nobody running a
    > machine like that can realistically expect good performance without hand
    > tuning stuff anyway

    I would think the guts of PIO block transfer would have to be protected
    anyway, but that's a very small part of the code.

    bill davidsen <>
    CTO, TMR Associates, Inc
    Doing interesting things with little computers since 1979.

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