"AGP connectors and slots are physically keyed to specify the signalling voltages the device is capable of operating at. AGP specifies two keys, a 3.3V key and a 1.5V key. Unfortunately they added a third voltage, 0.8V. If a device operates at 0.8V it uses the 1.5V key and must be tolerant of 1.5V signalling, but not necessarily capable of operating at 1.5V. A key is manifested as a raised area in a female connector or slot and a gap or absence of pins in a male connector. The keys physically prevent an electrically incompatible AGP video card from being inserted into an AGP slot."
Se mi dici che la scheda non entra fisicamente nello slot agp è un altra cosa.
Ma questa cosa la sapevo da tempo, infatti ho diverse schede agp 8x, quindi a 0,8v, ma regolarmente su slot agp a 1,5v e universali a 3,3 e 1,5.
questa è una mia vecchia scheda madre intel:

supporta schede agp 1x/2x, ma ci ha girato sopra una 9200SE AGP 8x