christos@zoulas.com said:
> > What makes an ID to the devices' primary ID | is that the vendor has
> > put it at a special place.
> 
> It has to give it a special tag. 

Yes - this is how it works for ISA-PnP. The PnP BIOS doesn't
use the "Logical Device ID" (obviously because there is no
need to put multiple devices into one ressource block),
so the "Device Product Identifier" at a fixed position in
the header is used there.

> I believe that vendors get assigned 3 letter ids, and the PNP id's are
> allocated by consensus.

The "consensus" might be Microsoft's dictate - at least the only
list os PNPnnnn IDs I found was at their site.

Wrt the use of vendor vs PNPnnnn IDs: might it be possible that
ISAPnP devices always use vendor IDs in the "Vendor ID" field
(at the very beginning of the ressource data), but are free to
use any ID as "Logical Device ID"?

best regards
Matthias