Re: LinkSys LNE100TX Card and EPROM Burner

[Ken Yap <ken@nlc.net.au>]

>would make sense. Does anyone know for sure how this works? I am 
>presuming the PCI card doesn't do the checking.

It's the BIOS that does the checking. The gory details are in the PnP BIOS
specs at the Phoenix site I think, but the PCI specs allow the BIOS to
control the PCI device to map the boot ROM into the address space of the
CPU. Then it examines the boot ROM header for a PCI and PnP signature. The
BIOS can also read the PCI vendor and device ID registers. So the BIOS
can do the comparison and then mark the ROM as an extension BIOS ROM to
be executed if it passes the tests.  There are provisions for backward
compatibility with legacy ROMs and all that. Very hairy. I find trying
to read the spec is very good for insomnia. :-)

>This explains why sometimes a floppy image will work, but an EPROM will 
>not work. The floppy image gets loaded by the BIOS no matter what, 
>whereas the EPROM image only loads if its PCI codes match the cards.

Yes.

I've just been reading the 21041 specs and I think I can figure out how
to do media switching (10BaseT/10Base2). I'll have a look to see if the
method is common across all Tulip chips.
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