RE: PCI-ISA bridges and ISAPNP

[Lame Brooks-G14738 <Brooks_Lame@mcg.mot.com>]

> > However, it seems that the PCI bridge responds to address 
> 279h for writes
> > and reads (on some mainboards), which obviously causes a conflict.
> > Since PCI tends not to have two devices at the same 
> location, one responding
> > to reads and one responding to writes, does this basically 
> mean that I can't
> > use location 279h?

Dan brought up the point that the PCI--ISA bridge generally should be
subtractively decoding 278~27Fh.  However, there are some chipsets,
primarily designed for use with a second 'docking' PCI--ISA bridge that uses
subtractive decoding; so, the first bridge does positive decoding.  

Some questions: on the motherboard you are having trouble with, is the
PCI--ISA bridge positively decoding reads to 279h?  Or, is your device
positively decoding writes?  Or, is your device waiting too long to claim
the cycle?  How about using 3BC~3BFh?  If you are using a Windows device
driver, does your device even _need_ to be at a legacy address?  I'm not a
Windows guru, but I would hope that if the PCI base class, sub class, and
register interface bytes say the device is a parallel port, that Windows
would recognize it as such.
--BrooksL