4770 Crossfire x16 vs. x8

[Echon]

Hi.

Does x16 make a difference compared to x8 with two of these cards? My motherboard, M4A79T Deluxe, has four PCI-E slots, but the two x16 ones are too far apart to reach with the crossfire bridge. I even have one of the longer cables.

My CPU is an AMD Phenom II X4 955 and my maximum resolution is 1680x1050. I play a variety of new and older games but nothing as demanding as Crysis. Fallout 3 is likely the heaviest at the moment.

 

[daedalus685]

No, x8 is more than enough for anything out today. Might handicap the next gen dual GPU cards though..b nothing to worry about for 4770's

 

[Echon]

Great, thanks.

 

[Echon]

So for some reason only one of these cards is being detected according to both CCC and GPU-Z. They both have additional power from the PSU, are connected with two crossfire bridges and catalyst 9.6 has been uninstalled and reinstalled since then. However, when I enter Windows (XP) I am told new hardware has been found which I assume is the second card. What is wrong here and what do I do?

 

[daedalus685]

Does device manager see the second card? Does it apply teh drivers to it correctly?

FYI, you only need one bridge to crossfire.

 

[Echon]

No, apparently that unknown device is related to the onboard audio. The device manager cannot see the second card.

 

[daedalus685]

Make sure any settign in the bios to enable the second PCIe slot are selected. Double check the card is seated correctly, and ensure both cards function on their own.

 

[Echon]

That last suggestion of yours was spot on. The second card provides no signal. Damn.

 

[redgarl]

You will notice no difference... it would only matter if you were using 2 GTX295... even there, I don't know.

What we learned is that SLI and Crossfire are extremely powerful solution with middle and middle high-end card, but two GTX295 or 4890 hurt performances.

Not normal that a core i7 perfoms better with two GTX260 over two GTX295 (check tomshardware latest budget PCs, 1300$ and 2000$)

 

[daedalus685]

Answer to his original question was already taken care of red

Also, crossfire provides about the same scaling throughout the lineup. It is not as good with a third and fourth GPU though. But, the thing that changes is the bang for your buck obviously goes down the higher end you go, double that and many would have a hard time justifying it.