Hi Uwe As much as for AVStream type of drivers go it's like that: at boot the PCI slot number is used, but if the user installs the cards than there is really no order that is correct -> ok there is if you remove both entrances in DeviceManager and then press right button -> "Scan for hardware changes". Than the PCI slot number is used. Anyway if 1 card is already installed and you want to install the other -> the system can uninstall the first one -> install the second and then install the first one again. So it's a mess. So for AVStream driver the serial number is correct only at boot time, but then again you shouldn't use the serial number -> it's a bad thing -> what happens if your first card is uninstalled and the system still supports the second -> then the serial number is wrong. Anyway in our driver we operate everything with class and card pointers and don't use the serial at all -> so if you need serial you get it every time you need it. It's much more safe that way. Good luck Waldemar uk> I'm developing a WDM driver for a soundcard. It's uses portclass uk> (WAVE_CYCLIC). If install more than one card of the same type, windows uk> adds "(2)" to the device names (friendly names). My question is how does uk> Windows detect which is the first card and which the second one. What uk> agorithm is used? I'm a little bit confused, because it's _always_ uk> different from what I expect. uk> Does it depent on the PCI slot number? uk> Does it depend on the order the drivers are loaded? (seems not) uk> Thanks Uwe uk> ****************** uk> WDMAUDIODEV addresses: uk> Post message: mailto:wdmaudiodev@xxxxxxxxxxxxx uk> Subscribe: mailto:wdmaudiodev-request@xxxxxxxxxxxxx?subject=subscribe uk> Unsubscribe: mailto:wdmaudiodev-request@xxxxxxxxxxxxx?subject=unsubscribe uk> Moderator: mailto:wdmaudiodev-moderators@xxxxxxxxxxxxx uk> URL to WDMAUDIODEV page: uk> http://www.wdmaudiodev.de/ ****************** WDMAUDIODEV addresses: Post message: mailto:wdmaudiodev@xxxxxxxxxxxxx Subscribe: mailto:wdmaudiodev-request@xxxxxxxxxxxxx?subject=subscribe Unsubscribe: mailto:wdmaudiodev-request@xxxxxxxxxxxxx?subject=unsubscribe Moderator: mailto:wdmaudiodev-moderators@xxxxxxxxxxxxx URL to WDMAUDIODEV page: http://www.wdmaudiodev.de/