Call me Mr. Skeptical but I can't possibly imagine why someone would flash a card out of a Mac Pro. It's worth far more as a Mac Pro card than it is as a PC card; everybody wants to know how they can use a cheap PC card in a Mac, not vice-versa. I'm having great difficulty constructing a Google search string that gives me any clear information about whether you could even theoretically use the first-gen Mac Pro cards in anything else.
I did find this discussion that implies that the X1300/X1900XT cards are indeed *very* Mac Pro specific; they have a 32 bit EFI BIOS, that won't work with a generic UEFI BIOS, and also says the legacy BIOS that's referenced when running "Bootcamp", IE, BIOS emulation, actually resides in the host machine, not the card. If this is all true... and as bass-ackward as it is I can pretty much believe it, then yes, no video would be expected behavior. (I would expect the PC to produce some error beeps, however, unless the card is so shmucked it's preventing the machine from POST-ing at all.
So what did the auction for this card say exactly, anyway? Did they *say* it was for a G5, or just that it was a "Mac video card", or...?
What I would probably try at this point is putting the card in a PC with a second video card in it, seeing if you can get the machine to boot that way, and determine if the card is being detected at all. (For instance, if you can boot Linux grep through "dmesg" to see if it detected anything, run "lspci", etc.) IF it shows up, well, you can try banging on it with a flash utility. Unless you have a 2006-2007 Mac Pro to try it in and see if it works there you're really shooting in the dark. (My guess is if it didn't work in the Mac Pro it's DOA, period.)
I did find this discussion that implies that the X1300/X1900XT cards are indeed *very* Mac Pro specific; they have a 32 bit EFI BIOS, that won't work with a generic UEFI BIOS, and also says the legacy BIOS that's referenced when running "Bootcamp", IE, BIOS emulation, actually resides in the host machine, not the card. If this is all true... and as bass-ackward as it is I can pretty much believe it, then yes, no video would be expected behavior. (I would expect the PC to produce some error beeps, however, unless the card is so shmucked it's preventing the machine from POST-ing at all.
So what did the auction for this card say exactly, anyway? Did they *say* it was for a G5, or just that it was a "Mac video card", or...?
What I would probably try at this point is putting the card in a PC with a second video card in it, seeing if you can get the machine to boot that way, and determine if the card is being detected at all. (For instance, if you can boot Linux grep through "dmesg" to see if it detected anything, run "lspci", etc.) IF it shows up, well, you can try banging on it with a flash utility. Unless you have a 2006-2007 Mac Pro to try it in and see if it works there you're really shooting in the dark. (My guess is if it didn't work in the Mac Pro it's DOA, period.)