Originally Posted by kevineugenius
So what is the difference between 7800go and 7800gtx? The E1705 with x1400 is PCI-E... Are all mobile 7800 cards PCI-E? 6800s came both AGP and PCI-E, but I don't know about 7800s first hand. I would assume, since i9300s had 7800 cards available (but i9300 was not PCI-E) that some 7800s are not PCI-E... Another something to think about.
Edit: just in case someone goes to look it up, the i9400 is also PCI-E. Another note, the E1505 comes with x1400 option as well, but it is NOT PCI-E. If there are indeed two different 7800 cards, could one upgrade an E1505 with an AGP 7800 and an E1705 with the PCI-E 7800?
PCI-E is just used by Dell as a specification of the signals going over this bus.
The connector itself and the positioning of the signals on the connector are fully according to Dell specs and aren't interchangeable with any other PCI-E connector.
Dell can even use the same connector on two different laptops, but change the position of the signals. Mechanically it looks the same, but electrically it does not work.
To answer the question if the 7800Go and 7800Go GTX are electrically interchangeable: this will only be the case if the PCI-E connector AND the monitor connector have the same pin layout.
From a mechanical point of view, they are completely interchangeable, apart from some binding post that could be in the way, but can be unsoldered.
I have tried a 6800Go in a 9400, but it did not work. Windows XP did not find new harware, and there was no single message on the LCD screen, not even the Nvidia Bios message at startup.
So either the PCI-E bus has a different layout, or the pinning of the monitor connector is different.
Since the 6800Go and the 7800Go GTX can both be used in the 9300, I am afraid that the 7800Go GTX also fails to work in a 9400 because some electrical pin layout is different to the 9300.