Re: [PARPORT] little confusion about register 0x3f0 0x3f1

From: Gunther Mayer (
Date: Wed Dec 11 2002 - 14:04:55 EST

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    Peter Asemann wrote:
    > I've found out that the parallel port driver code accesses registers 0x3f0
    > 0x3f1. It searches some SuperIO extended function registers. But normally
    > there should be fdc0 on that address.
    > So... will the Linux fdc drivers also scan for an device there?
    > Are the special registers of SuperIO chipsets always at that address?

    No. See for more.

    > What is the difference in the reaction of an fdc and a parallel port?
    > The ideal answer would be "0x3f0 / 0x3f1 are always reserved for the SuperIO
    > chips, no other driver ever needs them."

    0x3f0 is
    - read-only for fdc.
    - write-only for some superio chips (get the Winbond W83877 datasheet and others).

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