I tried inserting the following boot options in Ubuntu while in grub:
vga=normal ( also tried vga=318 )
in various combinations, and also trying with the recovery boot options as well, all to no avail (and removing 'quiet' and 'splash' to see what might be going on). After hitting 'b' to boot, the system reports it is booting from the selected disk, prints "Starting up ..." and after that, nothing. No disk activity seen and system is hung.
The most telling fault with this card & machine is that one cannot enter the bios by pressing F2. If you try that, you get a blank screen.
I conclude the problem is an electrical motherboard incompatibility.
I found that the PCI 2.1 and 2.2 specs say:
The maximum power allowed for any PCI board is 25 watts, and represents the total power drawn from all power rails provided at the connector (+5V, +3.3V, +Vi/o, +12V, -12V, +3.3Vaux).
But the PNY engineer told me the idle power draw for the 8400GS card is 31 watts! So it is not even compliant with the PCI electrical standard.
I did notice the heatsink of the 8400 got noticeably more warmer than that of the 6200, despite having done no real work!
So this card is going back. The PNY 8400GS just isn't going to work with this machine. Dunno how it managed to work with other Motherboards - perhaps their PCI connectors are more beefy?
For what it is worth, these guys have had similar problems:
So this leaves me with staring at the empty AGP connector on this PC and wondering if ATI will ever provide a linux driver that accelerates HD decoding ...