For [MSI](http://en.wikipedia.org/wiki/Message_Signaled_Interrupts)(Message Signaled Interrupts), [the IRQ value in the Windows Device Manager is large or negative](http://social.technet.microsoft.com/Forums/en-CA/winservergen/thread/e43c2c97-6e87-40c9-81f2-d1de219fb55b).

Why is this so?