Pcie x16 slot split over 2 x8 slots performance

febisfebi

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unfortunately my motherboard (MSI DKA790gx) has 2 pcie slots with crossfire enabled, but is limited to 2 x8 lanes when 2 cards are used, and one x16 when one card is used. I am wondering if this will degrade performance much when using 2 radeon hd 4850's such as this one:
http://www.newegg.com/Product/Product.aspx?Item=N82E16814127401
I can get 2 of them for less than the cost of a gtx 260, which is what i'll probably get if I decide to use just one card.
can someone help me out on decidng which to get? i'm really leaning towards nvidia, as most games I will play perform better with them, but I am certainly open to ati if I can get more performance for the same money.
Now, honestly, who designed this motherboard... first, the ram slots are too close to the cpu socket, so when using a performance cooler it has to be put on backwards, so it blows toward the front of the case.
second, the pcie setup is like this:
top: x16
2nd: x4
3rd x4
4th x8
pci
pci
with no space between the bottom x8 slot and the pci slots. so when using 2 cards that take up 2 slots each, theres an extra slot above the second one and it disables one of the 2 pci slots which I need both of. this would take an extra investment of a usb wifi card or tv tuner, whichever is cheaper. I wish I had bough a proper designed sli board, but I hadnt dreamed of using 2 video cards when i bought it, and the motherboard was a steal at $85.
 

febisfebi

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heh, your right, I just guessed, as I am not using them and dont plan on using them anyways.

looks like I could run dual 4830's for $160 or so. what kind of performance decrease would this involve over dual 4850's? and again compared to the gtx 260
 

spathotan

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4830's in Crossfire is a good setup. They will top a 4870, GTX260 as well more than likely. Also some of the 4830's can overclock to a 4850 if you can keep temps undercontrol and stable.
 

febisfebi

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febisfebi

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his one is nice, I looked at it, but quite a bit more expensive. I am trying to keep this under the cost of a gtx 260 so I can justify it hehe. The MSI I chose for the one slot size, as my second pcie slot is right next to where my precious 2 pci slots start. I have a wifi card and tv tuner. I dont want to resort to usb for either of those.
Also the asus card I listed (overclockec at 680 mhz) with a silly looking fan is only $110 open box right now. HIS makes a one slot 4850, but its more expensive. anyone have experience with any of these cards? or an answer to the one card factory overclocked, one card base question?
 

febisfebi

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thes setup should also be considerably cheaper than a 4850 x2 at $~300. the sapphire one has quad dvi. this is nice, especially because crossfire currently dosen't support dual monitors, let alone quad monitors :)